出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/12/18 01:47:08」(JST)
| この項目では、音楽ユニットについて記述しています。化学 (Chemistry)については「化学反応」をご覧ください。 |
| この存命人物の記事には検証可能な出典が求められています。信頼できる情報源の提供に協力をお願いします。存命人物に関する出典の無い、もしくは不完全な情報に基づいた論争の材料、特に潜在的に中傷あるいは有害となるものはすぐに除去する必要があります。（2011年2月） |
| CHEMISTRY | |
|---|---|
| 基本情報 | |
| 別名 | ケミ |
| 出身地 | 日本 |
| ジャンル | J-POP、R&B |
| 活動期間 | 2001年 - 2012年（活動休止） |
| レーベル | デフスターレコーズ |
| 事務所 | ソニー・ミュージックアーティスツ |
| 公式サイト | CHEMISTRY OFFICIAL WEBSITE |
| メンバー | |
| 川畑要（ボーカル） 堂珍嘉邦（ボーカル） |
|
CHEMISTRY（ケミストリー）は、日本の男性ツインボーカルユニット。所属レーベルはデフスターレコーズ。所属事務所はソニー・ミュージックアーティスツ。公式ファンクラブ名は「chemistry club」である。
テレビ東京のオーディション番組『ASAYAN』（当時司会のナインティナイン、中山エミリ）が行った男性ボーカリストオーディションで選ばれた2人により結成。2人の声が「音楽的化学反応」を起こすことを期待して、2001年1月1日にアメリカで松尾潔からCHEMISTRYと名づけたことを聞かされた[1][2]。
| かわばた かなめ 川畑要 |
|
| 本名 | 川畑 要 |
|---|---|
| 生年月日 | 1979年1月28日（34歳） |
| 出生地 | 東京都葛飾区 |
| 国籍 | 日本 |
| 民族 | 日本人 |
| 血液型 | A型 |
| 職業 | 歌手、俳優、ナレーター |
| ジャンル | 歌手 |
| 活動期間 | 2001年 - |
| 配偶者 | 高橋美紀（2008年 - 2013年） |
| 家族 | 娘（長女） |
| 主な作品 | |
| ドラマ『ハングリー!』 | |
| 備考 | |
| 2012年ドラマ『ハングリー!』でドラマ初出演を果たす。 | |
|
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1979年1月28日生まれ。身長173cm、血液型：A型。
東京都葛飾区出身。葛飾区立亀有中学校卒業。中学校卒業後アルバイトを転々とし、19歳頃から本格的に歌手を志す。オーディション時は建築関連のアルバイトをしており、東京ディズニーランドの「プーさんのハニーハント」の工事に携わった[3]。背中と両腕にタトゥーを入れている。2008年3月6日、「This Night」のPVで共演したモデルの高橋美紀と結婚、同年9月17日に第1子（長女）が誕生。2013年5月3日、離婚。
体を鍛えることを趣味としキックボクシングジムに通っている。日本酒・漬物を苦手とし、もんじゃ・韓国料理、漫画は『ONE PIECE』を好み、好きなアーティストは2PM、クリス・ブラウンでありアメリカのR&B、K-POPアーティスト知識に詳しい[4]。親交の深い芸能人は塚本高史、阿部サダヲである。朗読劇では乱視の為眼鏡をかけている。ギターを演奏できる。立ち位置は向かって右。川畑のファンクラブ名は「かなめ屋」。
かつては帽子がトレードマークの一つとなっていた。コレクションは100種類近くにもなるという。なお、メンバーの心境等を綴った『ひとりひとり』では「帽子を被らない姿を見せたくない」旨のことを語っていたが、2008年夏以降、段階的に帽子を被らない姿を見せるようになり、2013年現在はほぼ帽子なしでメディアに登場している。なお、帽子を被り始めた頃は坊主頭だったとのことだが、それがはっきりわかるような写真・映像は公開されていない。また、デビュー前は長髪にしていたことがある。現在の髪の長さは中程度で金色に染めている。
| 堂珍嘉邦 | |
| 本名 | 堂珍嘉邦 |
|---|---|
| 生年月日 | 1978年11月17日（35歳） |
| 出生地 | 広島県安芸高田市 |
| 国籍 | 日本 |
| 民族 | 日本人 |
| 血液型 | O型 |
| 職業 | 歌手、俳優 |
| ジャンル | 歌手 |
| 活動期間 | 2001年 - 現在 |
| 配偶者 | 堂珍敦子 |
| 家族 | 4児 [5] |
| 主な作品 | |
| 映画『真夏のオリオン』 | |
| 備考 | |
| 2009年、映画『真夏のオリオン』で映画初出演を果たす。 | |
|
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1978年11月17日生まれ。身長174cm、血液型：O型。
広島県高田郡八千代町（現・安芸高田市）出身。「堂珍」姓は非常に珍しく日本に1軒（一族だけ）と思われる名字[6]。広島県新庄高等学校卒業。高校在学時より本格的に歌手を志すようになる。高校卒業後、テレビ新広島のAD、広島市民球場での警備員、プール監視員、コンビニ等のバイトをしながら、オーディションをいろいろ受ける。ザ・ジャパン・オーディションやASAYANのpool bit boysオーディションでは、いいところまで残るが勝てなかったという。2004年、森田あつ子と結婚し、現在4児。2009年、映画『真夏のオリオン』で映画初出演を果たした。2011年、「自分自身の成長がないと、歌も良くなっていかないと思う、音楽活動以外の活動も視野に入れたい」と述べ、[7]辻仁成が脚本・演出・音楽を担当する音楽劇「醒めながら見る夢」に主演。[8][9]。2010年10月よりJTのルーツ発売10周年記念のCMソング「根の歌」を歌うユニット「コーラスジャパン」に参加。2011年3月11日に発生した東北地方太平洋沖地震を受けての特別番組、『FNS音楽特別番組 上を向いて歩こう 〜うたでひとつになろう日本〜』に同ユニットで出演した際には、他の出演者と同じくギャラを義捐金として寄付している。
一時期は睡眠時間を削る程のゲーマーであり、プレイステーション3、Xbox 360、ニンテンドー3DSといったメジャーなゲーム機を数多く所有する。広島東洋カープファンであり、始球式を2回行った。趣味は前述のゲームのほか写真撮影。尊敬するアーティストは吉井和哉。ピアノ・ギターを演奏する。 立ち位置は向かって左。堂珍のファンクラブ名は「Drunkboat」。
1999年8月、『ASAYAN』の企画「男子ボーカリストオーディション」の1次審査に川畑・堂珍共に大阪会場で参加し通過[10]。その後、最終選考まで進出。2000年12月15日、オーディション最終選考の一環で発売された仮デビューシングル「最後の夜」（当時のユニット名は「ASAYAN超男子。川畑・堂珍」）が、オリコン初登場9位を記録。2001年1月1日、オーディション最終選考で川畑と堂珍の2人が選ばれる。デュオを選ぶという見地にたって選考された結果、個々の表現力と潜在能力の高さは勿論のこと2人が一緒になったときの化学反応の素晴らしさから、この川畑･堂珍デュオが選ばれることとなった。その後、2001年1月21日の放送でユニット名が「CHEMISTRY」に正式に決定する。
2001年3月7日にシングル「PIECES OF A DREAM」でデビューし、発売6週目でオリコン1位を獲得。これはジャニーズ事務所所属のアイドルを除けば男性ボーカルグループでは21年ぶりという快挙であった。その後ロングヒットとなり、発売15週目にミリオンセラーを達成した。同年11月には初のオリジナルアルバム『The Way We Are』を発売、トリプルミリオンを記録する。このアルバムのセールスで、オリコンに於ける男性アーティストのデビューアルバムとしての歴代1位記録を樹立した。また、この年には『第52回NHK紅白歌合戦』に初出場し、この年の紅白最高視聴率52.4パーセントを記録している[11]。
2002年1月、当時デビュー前だったSoweluと共に日本代表として、韓国のアーティスト（Brown Eyes、リナ・パーク）と合同ユニット「Voices of KOREA/JAPAN」を結成。その後3月にはサッカーW杯日韓大会のテーマ曲を収録したシングル「Let's Get Together Now」を発売。5月30、31日にソウルで開催されたW杯前夜祭・開会式にも参加し楽曲を披露している[12]。
2002年12月、シングル「My Gift to You」発売。世界初の着うたソングに起用される[13][14]。翌2003年1月には2作目のオリジナルアルバム『Second to None』を発売。オリコン週間アルバムチャートで2週連続の第1位を獲得。また、ミリオンセールスも記録し2003年年間アルバムランキングでも1位を獲得した。これにより、オリコンに於ける男性アーティストとしては初となるデビューアルバムからの連続での初登場・ミリオン突破記録を樹立した[14]。
2003年6月、リミックス曲を中心に収録した企画アルバム『Between the Lines』を発売。このアルバムをもって、プロデューサー松尾潔の元から離れ、セルフプロデュースへ移行する。
その後2003 - 2004年にかけシングルを3枚リリースし、2004年2月には3作目のオリジナルアルバム『One × One』を発売した。また2005年1月にはバラード曲を中心に収録した企画アルバム『Hot Chemistry』を30万枚限定発売。ともにオリコン初登場1位を獲得し、これにより1stアルバムからの連続初登場首位記録においてKinKi Kids（6作連続）に次ぐ歴代2位（5作連続）を記録した。
2005年10月、Crystal Kayとのコラボレーション楽曲「Two As One」を「Crystal Kay × CHEMISTRY」名義でシングルとして発売。翌月に発売された16thシングル「almost in love」では、「CHEMISTRY × Crystal Kay」名義による別バージョンを収録している。更に同11月には1年9ヶ月ぶり、4作目のオリジナルアルバム『fo(u)r』を発売、オリコンチャートで2位を獲得した。
およそ10ヶ月の充電期間の後、槇原敬之プロデュースの「約束の場所」と「遠影 feat. John Legend」を2ヶ月連続リリース。2006年11月にはそれらを先行シングルとする初のベストアルバム『ALL THE BEST』を発売。このアルバムにはボーナス・トラックとして、松尾潔を再びプロデューサーに迎えての新曲「Top of the World」も収録された。
2008年1月、2年2ヶ月ぶりとなるオリジナルアルバム『Face to Face』を発売し、オリコンチャートで3位を獲得。これでオリジナルアルバムすべてがTOP3にチャートインすることとなった。さらに11月にはバラードコレクションアルバム『Winter of Love』を、翌年3月には他アーティスト等とのコラボレーションを示す「a CHEMISTRY joint」の集大成アルバム、『the CHEMISTRY joint album』を発売した。「a CHEMISTRY joint」について川畑は「音楽で他のアーティストとジョイントする事も、お互いがソロで音楽じゃない部分で何かにトライした時とか、今までやってきた事を見直せるようなそういうものがあったらいいな」と述べている [15]。
2010年2月、6枚目のオリジナルアルバム『regeneration』を発売し、その後行われたライブツアーではRui・Keito・Dee・Chihiroをバックダンサーとして起用し[16]、ツアー内では共にダンスを披露した。ツアー最終日に彼ら4人とのデビュー10周年に向けての期間限定ユニット「CHEMISTRY + Synergy（ケミストリープラスシナジー）」結成を発表し、8月18日にはシングル「Shawty」を発売。
2010年、韓国映画『無籍者（無敵者、무적자、邦題「男たちの挽歌 A BETTER TOMORROW」）』のハングル版全世界主題歌「a better tomorrow」を担当。[17]、2010年9月8日「무적자」試写会出席の為渡韓[18]、韓国のSONY MUSICにて9月9日記者会見を行った[19][20]。「a better tomorrow」は「CHEMISTRY + Synergy」の第2弾シングル「Keep Your Love」のカップリングとして収録された。
11月、マカオで開催されたMnet『Mnet Asian Music Awards』ではPerfumeと共に出演し、「Best Asian Male Artist」を受賞。
12月13日、CHEMISTRY + Synergy名義での新曲発表休止、Deeの脱退、Synergy活動継続を公式サイトにて発表した。
2011年3月には自身2枚目となるベストアルバム『CHEMISTRY 2001-2011』を発売し、それを携えた全国ライブツアーが予定されていたが、同年3月11日に発生した東北地方太平洋沖地震の影響を受け、複数の地方公演が中止、延期となった。なお、「根の歌」（コーラスジャパン）・「My Gift to You」は「レコチョク」の「アーティストチャリティー」となった。
2011年7月29日・30日にアメリカのボルチモアにて開催されたOtakonに出演しライブに5000人、サイン会に1000人動員、Q&Aを行った[21][22][23]。
2011年からはソロ活動を本格的に始動させ、堂珍の音楽劇『醒めながら見る夢』主演、5・6月に東名阪で行われたファンクラブ会員限定のソロライブに加え、川畑は10月に、堂珍は12月に東名阪にてライブを開催[24][25][26]。 ソロ活動について川畑は「ソロでお互いの良さを築いて、それがCHEMISTRYに反映されればいいな」[27]と語っている。吉井和哉から「いつロックやるんだよ？」[28]などと言われた堂珍は「ロックやりたい。ケミで色々培ってきたもの、逆にケミをやっているから自分が見えないものをソロで吐き出したりそぎ落として」[29]と述べている。
2012年4月7日、コンサートツアー『CHEMISTRY TOUR 2012 -Trinity-』の沖縄での最終公演で、CHEMISTRYの活動をいったん休止してそれぞれのソロ活動に専念することを発表[30]。翌日4月8日には、活動休止についてのメッセージが公式サイトに掲載された[31]。ライブアルバム「CHEMISTRY TOUR 2012 〜Trinity〜」が2012年11月21日発売。
1月クールに放送されたテレビドラマ『ハングリー!』でドラマ初出演を果たした[32]川畑は、6月16・17日開催の朗読「サマーウォーズ」に出演[33]。6月24日、川畑はTwitterにて1週間内に候補曲「Flyin' to the sunrise」と「TOKYO GIRL」（2010年8月27日、「JOY LIVE! supported by Future Tracks→R〜JOY 1st Anniversary〜」にて「KANAME」として披露、振付はRuiが担当[34]）の試聴公開、意見を募集。「TOKYO GIRL」が10月3日発売、2013年2月1日公開映画「ベルセルク 黄金時代篇III 降臨」エンディングテーマ「breakthrough」が収録されている「breakthrough/Let's Say I Do 」を1月30日発売、アルバム「0」を6月12日に発売、6月22日バンコクにて「J POP SIGNATURE in BANGKOK」に参加[35][36][37]、「KANAME KAWABATA LIVE TOUR 2013 "0"」を7月5日より開催。
川畑が出演するライブではRui、KEiSUKE、Nosukeが参加。自身が出演する2014年2月インドネシア公開予定の映画「BUSHIDO SPIRIT」のOSTではNovita Dewi Marpaungとのデュエットで五輪真弓の「KOKORO NO TOMO」カバーを収録予定である[38]
一方、休止発表後しばらく表立って動きがなかった堂珍は、2012年7月25日、新レーベル「Scalear」、「キノシタ・マネージメント」への移籍を発表した。オフィシャルウェブサイトを立ち上げ、Twitterのアカウントも一新した。自らの音楽性を耽美＋アンビエント＝耽美エントRockと命名したとキャッチフレーズ発表。8月6日、仙台のフリーライブDate fm 夕涼みコンサート2012で久々に公の場に登場。 9月からは、interFMでレギュラー番組Now What Can I see?開始。 10月8日に渋谷公会堂でソロ初のワンマンライブ『A La Musique』を行い、11月14日にソロデビューシングル「Shout/hummingbird」が発売、2013年2月6日に2ndシングル「handle me right」、2月27日にアルバム「OUT THE BOX」が発売。アルバムを引っさげ『TOUR 2013 "OUT THE BOX"』を行う。7月10日にツアーDVD「堂珍嘉邦 TOUR 2013 “OUT THE BOX”at Zepp DiverCity Tokyo」と3rdシングル「Euphoria」を発売、9月「堂珍嘉邦 TOUR 2013 "OUT THE BOX 〜in late summer〜"」開催、2014年5月主演映画「醒めながら見る夢」公開予定[39]。2013年10月「Scalear」は「キノミュージック」内のレーベルとなる。 堂珍のライブではかどしゅんたろう、Ali(MONORAL)、堀向彦輝、セバスチャン(BULL ZEICHEN 88)/パブロ(Pay money To my Pain)が参加している。2014年3月5日に新作アルバム「Bronze Caravan」を発売予定。
※「順位」はオリコンチャートの順位。
| 枚 | 発売日 | タイトル | 順位 | 備考 |
|---|---|---|---|---|
| 1st | 2001年3月7日 | PIECES OF A DREAM | 1位 | |
| 2nd | 2001年6月6日 | Point of No Return | 1位 | |
| 3rd | 2001年10月11日 | You Go Your Way | 1位 | |
| 4th | 2002年5月9日 | 君をさがしてた 〜New Jersey United〜 | 2位 | |
| 5th | 2002年7月17日 | FLOATIN' | 1位 | |
| 6th | 2002年11月13日 | It Takes Two／SOLID DREAM／MOVE ON | 1位 | |
| 7th | 2002年12月18日 | My Gift to You | 4位 | [40] |
| 8th | 2003年8月6日 | アシタヘカエル／Us | 1位 | LG |
| 9th | 2003年11月19日 | YOUR NAME NEVER GONE／Now or Never／You Got Me | 2位 | LG |
| 10th | 2004年2月4日 | So in Vain | 3位 | [41]、LG |
| 11th | 2004年7月7日 | mirage in blue／いとしい人(Single Ver.) | 4位 | LG |
| 12th | 2004年10月27日 | Long Long Way | 5位 | LG |
| 13th | 2004年12月1日 | 白の吐息 | 8位 | |
| 14th | 2005年2月23日 | キミがいる | 4位 | |
| 15th | 2005年7月27日 | Wings of Words | 2位 | |
| 16th | 2005年11月2日 | almost in love | 6位 | |
| 17th | 2006年10月4日 | 約束の場所 | 4位 | |
| 18th | 2006年11月1日 | 遠影 feat. John Legend | 9位 | |
| 19th | 2006年12月6日 | Top of the World | 28位 | [42] |
| 20th | 2007年4月25日 | 空の奇跡 | 9位 | |
| 21st | 2007年8月1日 | This Night | 13位 | |
| 22nd | 2007年10月24日 | 最期の川 | 4位 | |
| 23rd | 2007年12月5日 | 輝く夜 | 18位 | [43] |
| 24th | 2008年8月20日 | Life goes on | 12位 | |
| 25th | 2008年11月5日 | 恋する雪 愛する空 | 16位 | |
| 26th | 2009年2月18日 | a Place for Us | 21位 | [44] |
| 27th | 2009年11月4日 | あの日… feat. 童子-T／Once Again | 19位 | |
| 28th | 2010年1月27日 | Period | 12位 | |
| 29th | 2010年8月18日 | Shawty | 18位 | CS |
| 30th | 2010年11月3日 | Keep Your Love | 11位 | CS |
| 31st | 2011年2月16日 | a better tomorrow | 16位 | |
| 32nd | 2011年3月2日 | merry-go-round | 19位 | |
| 33rd | 2011年8月10日 | Independence | 17位 | |
| 34th | 2011年11月30日 | eternal smile | 19位 |
凡例
| 発売日 | タイトル | 順位 | 備考 |
|---|---|---|---|
| 2000年12月15日 | 最後の夜/My Cherie Amour | 9位 | 「ASAYAN超男子。川畑・堂珍」名義 |
| 枚 | 発売日 | タイトル | 順位 | 備考 |
|---|---|---|---|---|
| 1st | 2012年10月3日 | TOKYO GIRL | 8位 | |
| 2nd | 2013年1月30日 | breakthrough/Let's Say I Do | 20位 |
| 枚 | 発売日 | タイトル | 順位 | 備考 |
|---|---|---|---|---|
| 1st | 2012年11月14日 | Shout/hummingbird | 21位 | |
| 2nd | 2013年2月6日 | handle me right | 59位 | |
| 3rd | 2013年7月10日 | Euphoria | 53位 |
| 発売日 | タイトル | 備考 |
|---|---|---|
| 2002年3月13日 | Let's Get Together Now | 「Voices of KOREA/JAPAN」名義 |
| 2005年10月5日 | Two As One | 「Crystal Kay × CHEMISTRY」名義 |
| 枚 | 発売日 | タイトル | 順位 |
|---|---|---|---|
| 1st | 2001年11月7日 | The Way We Are | 1位 |
| 2nd | 2003年1月8日 | Second to None | 1位 |
| 3rd | 2004年2月18日 | One × One[45] | 1位 |
| 4th | 2005年11月16日 | fo(u)r | 2位 |
| 5th | 2008年1月30日 | Face to Face | 3位 |
| 6th | 2010年2月24日 | regeneration | 5位 |
| 7th | 2012年1月25日 | Trinity | 8位 |
| 枚 | 発売日 | タイトル | 順位 |
|---|---|---|---|
| 1st | 2003年6月18日 | Between the Lines | 1位 |
| 2nd | 2005年1月26日 | Hot Chemistry （30万枚完全生産限定盤） | 1位 |
| 3rd | 2008年11月19日 | Winter of Love | 7位 |
| 4th | 2009年3月11日 | the CHEMISTRY joint album | 10位 |
| 枚 | 発売日 | タイトル | 順位 |
|---|---|---|---|
| 1st | 2006年8月9日 | Re:fo(u)rm | 25位 |
| 枚 | 発売日 | タイトル | 順位 |
|---|---|---|---|
| 1st | 2006年11月22日 | ALL THE BEST | 1位 |
| 2nd | 2011年3月2日 | CHEMISTRY 2001-2011 | 6位 |
| 枚 | 発売日 | タイトル | 最高位 |
|---|---|---|---|
| 1st | 2012年11月21日 | CHEMISTRY TOUR 2012 〜Trinity〜 | 39位 |
| 枚 | 発売日 | タイトル | 最高位 |
|---|---|---|---|
| 1st | 2013年6月12日 | 0 | 24位 |
| 枚 | 発売日 | タイトル | 最高位 |
|---|---|---|---|
| 1st | 2013年2月27日 | OUT THE BOX | 52位 |
| 2nd | 2014年3月5日 | Bronze Caravan |
ライブ・ツアーは太字で示す。
| 楽曲 | タイアップ | 備考 |
|---|---|---|
| PIECES OF A DREAM | テレビ東京系『ASAYAN』 エンディングテーマ | |
| You Go Your Way | サントリー「BOSS」CMソング | 本人出演 |
| 君をさがしてた〜New Jersey United〜 | フジテレビ系ドラマ『ウエディングプランナー SWEETデリバリー』主題歌 | |
| Let's Get Together Now | FIFAワールドカップ 2002年公式テーマ曲 | |
| 明治チェルシーの唄 | 明治製菓「チェルシー」2003年CMソング | |
| Naturally Ours | 日本コカ・コーラ「爽健美茶」CMソング | |
| 恋するカレン | WOWOW CMソング | |
| It Takes Two | フジテレビ系ドラマ『ダブルスコア』主題歌 | |
| SOLID DREAM | フジテレビ系『めざましテレビ』テーマソング | |
| MOVE ON | ダイハツ工業「ムーヴカスタム」CMソング | 本人出演 |
| My Gift To You | KDDI「au ムービーメール」CMソング | 本人出演 |
| アシタヘカエル | 日本コカ・コーラ「爽健美茶」CMソング | |
| Us | ダイハツ工業「ムーヴカスタム」CMソング | 本人出演 |
| YOUR NAME NEVER GONE | ソニー「MDウォークマン/サウンドゲート」CMソング | |
| Now or Never | フジテレビ系アニメ『アストロボーイ・鉄腕アトム』第2期オープニングテーマ | |
| You Got Me | ダイハツ工業「ムーヴカスタム」CMソング | 本人出演 |
| Bound for Identity〜dear friend〜 | JR東日本 はやて1周年「北東北には色があるキャンペーン」CMソング | |
| Ordinary hero | ダイハツ工業「ムーヴカスタム」CMソング | |
| meaning of tears | サントリー「角瓶」CMソング | 本人出演 |
| mirage in blue | エフティ資生堂「シーブリーズ」2004年CMソング | |
| いとしい人(Single Ver.) | 映画『69 sixty nine』主題歌 | |
| Long Long Way | サントリー「角瓶」CMソング | 本人出演 |
| 白の吐息 | ||
| チャイム | セイコー「ルキア」CMソング | |
| ココロノドア | 映画『きみに読む物語』イメージソング | |
| キミがいる | 日本テレビ系ドラマ『87%』主題歌 | |
| Wings of Words | TBS系アニメ『機動戦士ガンダムSEED DESTINY』第4期オープニングテーマ | |
| Change the World | サントリー「角瓶」CMソング | 本人出演 |
| Here I Am | 海外ドラマ「LOST」シーズン1日本版テーマソング | |
| Two As One | トヨタ自動車「ウィッシュ」CMソング | |
| almost in love | TBS系『恋するハニカミ!』テーマソング | |
| 伝説の草原 | 『FIFAクラブワールドカップ2005』大会テーマソング | |
| 伝説の草原 (Patrick Stump Remix) | 映画『オープン・シーズン』日本語吹き替え版イメージソング | |
| 約束の場所 | 味の素「クノール」CMソング | |
| 遠影 feat. John Legend | 映画『オープン・シーズン』日本語吹き替え版挿入歌 | |
| クリスマスローズ | 味の素「クノール」CMソング | |
| Top of the World | 『FIFAクラブワールドカップ2006』大会テーマソング | |
| 空の奇跡 | シャープ「au AQUOSケータイ W51SH」CMソング | 本人出演 |
| 雨上がりの虹のように | 味の素「クノール」CMソング | |
| This Night | TBS系アニメ『地球へ…』第2期エンディングテーマ | |
| 最期の川 | 映画『象の背中』主題歌 | |
| 輝く夜 | 『FIFAクラブワールドカップ2007』大会テーマソング | |
| Life goes on 〜side K〜 | フジテレビ系アニメ『西洋骨董洋菓子店 〜アンティーク〜』オープニングテーマ | |
| Life goes on 〜side D〜 | フジテレビ系アニメ『西洋骨董洋菓子店 〜アンティーク〜』エンディングテーマ | |
| 恋する雪 愛する空 | 日清｢日清カップヌードルミルクシーフード｣TVCMソング | |
| キスからはじめよう | 映画『ブーリン家の姉妹』イメージソング | |
| ALIVE | 日本テレビ系『ズームイン!!SUPER』冬のお天気テーマ | |
| SUPERSTAR | 2009 TBS系プロ野球中継テーマ曲 | |
| Once Again | NHK連続テレビドラマ『チャレンジド』主題歌 | |
| レコチョクCM曲 | ||
| Period | TBS系アニメ『鋼の錬金術師 FULLMETAL ALCHEMIST』第4期オープニングテーマ | |
| Brandnew Season 〜夢の乗車券〜 | 「明光義塾」CMソング | |
| Our Story | セガ社ゲーム『戦場のヴァルキュリア2』主題歌 | |
| Crossing | TOYOTA「プレミオ」・「アリオン」イメージソング | |
| Shawty | テレビ東京系列『DANCE@TV』2010年8月度オープニングテーマ | |
| フジテレビ系『ウチくる!?』2010年8月度エンディングテーマ | ||
| 『MTV×DAM WANNASING KARAOKEE CHART TOP20』2010年8月度CMソング | 本人出演 | |
| Keep Your Love | テレビ東京系列『DANCE@TV』2010年10月度オープニングテーマ | |
| a better tomorrow | 2010年9月16日公開韓国映画『無籍者』全世界主題歌 | |
| merry-go-round | 2011年3月5日公開（配信/劇場）『機動戦士ガンダムUC』episode 3「ラプラスの亡霊」主題歌 | |
| eternal smile | 2011年サンリオクリスマスキャンペーンCMテーマソング | |
| Dreamy Life | 「BS258」Dlife開局イメージソング |
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Chemistry, a branch of physical science, is the study of the composition, properties and change of matter.[1][2] Chemistry is chiefly concerned with atoms and their interactions with other atoms - for example, the properties of the chemical bonds formed between atoms to create chemical compounds. As well as this, interactions including atoms and other phenomena - electrons and various forms of energy - are considered, such as photochemical reactions, oxidation-reduction reactions, changes in phases of matter, and separation of mixtures. Finally, properties of matter such as alloys or polymers are considered.
Chemistry is sometimes called "the central science" because it bridges other natural sciences like physics, geology and biology with each other.[3][4] Chemistry is a branch of physical science but distinct from physics.[5]
The etymology of the word chemistry has been much disputed.[6] The genesis of chemistry can be traced to certain practices, known as alchemy, which had been practiced for several millennia in various parts of the world, particularly the Middle East.[7]
| Chemistry |
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The word chemistry comes from the word alchemy, an earlier set of practices that encompassed elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism and medicine; it is commonly thought of as the quest to turn lead or another common starting material into gold.[8] Alchemy, which was practiced around 330, is the study of the composition of waters, movement, growth, embodying, disembodying, drawing the spirits from bodies and bonding the spirits within bodies (Zosimos).[9] An alchemist was called a 'chemist' in popular speech, and later the suffix "-ry" was added to this to describe the art of the chemist as "chemistry".
The word alchemy in turn is derived from the Persian word kīmīa (كيميا) which is already altered into its Arabic, al-kīmīā (الکیمیاء), form. In origin, the term is borrowed from the Greek χημία or χημεία.[10][11] This may have Egyptian origins. Many believe that al-kīmīā is derived from χημία, which is in turn derived from the word Chemi or Kimi, which is the ancient name of Egypt in Egyptian.[10] Alternately, al-kīmīā may be derived from χημεία, meaning "cast together".[12]
In retrospect, the definition of chemistry has changed over time, as new discoveries and theories add to the functionality of the science. The term "chymistry", in the view of noted scientist Robert Boyle in 1661, meant the subject of the material principles of mixed bodies.[13] In 1663, "chymistry" meant a scientific art, by which one learns to dissolve bodies, and draw from them the different substances on their composition, and how to unite them again, and exalt them to a higher perfection - this definition was used by chemist Christopher Glaser.[14]
The 1730 definition of the word "chemistry", as used by Georg Ernst Stahl, meant the art of resolving mixed, compound, or aggregate bodies into their principles; and of composing such bodies from those principles.[15] In 1837, Jean-Baptiste Dumas considered the word "chemistry" to refer to the science concerned with the laws and effects of molecular forces.[16] This definition further evolved until, in 1947, it came to mean the science of substances: their structure, their properties, and the reactions that change them into other substances - a characterization accepted by Linus Pauling.[17] More recently, in 1998, the definition of "chemistry" was broadened to mean the study of matter and the changes it undergoes, as phrased by Professor Raymond Chang.[18]
Early civilizations, such as the Egyptians[19] and Babylonians amassed practical knowledge concerning the arts of metallurgy, pottery and dyes, but didn't develop a systematic theory.
A basic chemical hypothesis first emerged in Classical Greece with the theory of four elements as propounded definitively by Aristotle stating that that fire, air, earth and water were the fundamental elements from which everything is formed as a combination. Greek atomism dates back to 440 BC, arising in works by philosophers such as Democritus and Epicurus. In 50 BC, the Roman philosopher Lucretius expanded upon the theory in his book De Rerum Natura (On The Nature of Things).[20][21] Unlike modern concepts of science, Greek atomism was purely philosophical in nature, with little concern for empirical observations and no concern for chemical experiments.[22]
In the Hellenistic world the art of alchemy first proliferated, mingling magic and occultism into the study of natural substances with the ultimate goal of transmuting elements into gold and discovering the elixir of eternal life.[23] Alchemy was discovered and practised widely throughout the Arab world after the Muslim Conquest,[24] and from there, diffused into medieval and Rennaissance Europe through Latin translations.[25]
Under the influence of the new empirical methods propounded by Sir Francis Bacon and others, a group of chemists at Oxford, Robert Boyle, Robert Hooke and John Mayow began to reshape the old achemical traditions into a scientific discipline. Boyle in particular is regarded as the founding father of chemistry due to his most important work, the classic chemistry text The Sceptical Chymist where the differentiation is made between the claims of alchemy and the empirical scientific discoveries of the new chemistry.[26] He formulated Boyle's law, rejected the classical "four elements" and proposed a mechanistic alternative of atoms and chemical reactions that could be subject to rigorous experiment.[27]
The theory of phlogiston (a substance at the root of all combustion) was propounded by the German Georg Ernst Stahl in the early 18th century and was only overturned by the end of the century by the French chemist Antoine Lavoisier, the chemical analogue of Newton in physics; who did more than any other to establish the new science on proper theoretical footing, by elucidating the principle of conservation of mass and developing a new system of chemical nomenclature used to this day.[29]
Prior to his work, though, many important discoveries had been made, specifically relating to the nature of 'air' which was discovered to be composed of many different gases. The Scottish chemist Joseph Black (the first experimental chemist) and the Dutchman J. B. van Helmont discovered carbon dioxide, or what Black called 'fixed air' in 1754; Henry Cavendish discovered hydrogen and elucidated its' properties and Joseph Priestley and, independently, Carl Wilhelm Scheele isolated pure oxygen.
English scientist John Dalton proposed the modern theory of atoms in his book (1803) Atomic Theory; that all substances are composed of indivisible 'atoms' of matter and that different atoms have varying atomic weights.
The development of the electrochemical theory of chemical combinations occurred in the early 19th century as the result of the work of two scientists in particular, J. J. Berzelius and Humphry Davy, made possible by the prior invention of the voltaic pile by Alessandro Volta. Davy discovered nine new elements including the alkali metals by extracting them from their oxides with electric current.[30]
British William Prout first proposed ordering all the elements by their atomic weight as all atoms had a weight that was an exact multiple of the atomic weight of hydrogen. J. A. R. Newlands devised an early table of elements, which was then developed into the modern periodic table of elements by the German Julius Lothar Meyer and the Russian Dmitri Mendeleev in the 1860s.[31] The inert gases, later called the noble gases were discovered by William Ramsay in collaboration with Lord Rayleigh at the end of the century, thereby filling in the basic structure of the table.
Organic chemistry was developed by Justus von Liebig and others, following Friedrich Wohler's synthesis of urea which proved that living organisms were, in theory, reducible to chemistry.[32] Other crucial 19th century advances were; an understanding of valence bonding (Edward Frankland in 1852) and the application of thermodynamics to chemistry (J. W. Gibbs and Svante Arrhenius in the 1870s).
Top: Expected results: alpha particles passing through the plum pudding model of the atom undisturbed.
At the turn of the twentieth century the theoretical underpinnings of chemistry were finally understood due to a series of remarkable discoveries that succeeded in probing and discovering the very nature of the internal structure of atoms. In 1897, J. J. Thomson of Cambridge University discovered the electron and soon after the French scientist Becquerel as well as the couple Pierre and Marie Curie investigated the phenomenon of radioactivity. In a series of pioneering scattering experiments Ernest Rutherford at the University of Manchester discovered the internal structure of the atom and the existence of the proton, classified and explained the different types of radioactivity and successfully transmuted the first element by bombarding nitrogen with alpha particles.
His work on atomic structure was improved on by his students, the Danish physicist Niels Bohr and Henry Mosely. The electronic theory of chemical bonds and molecular orbitals was developed by the American scientists Linus Pauling and Gilbert N. Lewis.
The year 2011 was declared by the United Nations as the International Year of Chemistry.[33] It was an initiative of the International Union of Pure and Applied Chemistry, and of the United Nations Educational, Scientific, and Cultural Organization and involves chemical societies, academics, and institutions worldwide and relied on individual initiatives to organize local and regional activities.
The current model of atomic structure is the quantum mechanical model.[34] Traditional chemistry starts with the study of elementary particles, atoms, molecules,[35] substances, metals, crystals and other aggregates of matter. This matter can be studied in solid, liquid, or gas states, in isolation or in combination. The interactions, reactions and transformations that are studied in chemistry are usually the result of interactions between atoms, leading to rearrangements of the chemical bonds which hold atoms together. Such behaviors are studied in a chemistry laboratory.
The chemistry laboratory stereotypically uses various forms of laboratory glassware. However glassware is not central to chemistry, and a great deal of experimental (as well as applied/industrial) chemistry is done without it.
A chemical reaction is a transformation of some substances into one or more different substances.[36] The basis of such a chemical transformation is the rearrangement of electrons in the chemical bonds between atoms. It can be symbolically depicted through a chemical equation, which usually involves atoms as subjects. The number of atoms on the left and the right in the equation for a chemical transformation is equal (when unequal, the transformation by definition is not chemical, but rather a nuclear reaction or radioactive decay). The type of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws.
Energy and entropy considerations are invariably important in almost all chemical studies. Chemical substances are classified in terms of their structure, phase, as well as their chemical compositions. They can be analyzed using the tools of chemical analysis, e.g. spectroscopy and chromatography. Scientists engaged in chemical research are known as chemists.[37] Most chemists specialize in one or more sub-disciplines. Several concepts are essential for the study of chemistry; some of them are:[38]
In chemistry, matter is defined as anything that has rest mass and volume (it takes up space) and is made up of particles. The particles that make up matter have rest mass as well - not all particles have rest mass, such as the photon. Matter can be a pure chemical substance or a mixture of substances.[39]
The atom is the basic unit of chemistry. It consists of a dense core called the atomic nucleus surrounded by a space called the electron cloud. The nucleus is made up of positively charged protons and uncharged neutrons (together called nucleons), while the electron cloud consists of negatively-charged electrons which orbit the nucleus. In a neutral atom, the negatively-charged electrons balance out the positive charge of the protons. The nucleus is dense; the mass of a nucleon is 1,836 times that of an electron, yet the radius of an atom is about 10,000 times that of its nucleus.[40][41]
The atom is also the smallest entity that can be envisaged to retain the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state(s), coordination number, and preferred types of bonds to form (e.g., metallic, ionic, covalent).
A chemical element is a pure substance which is composed of a single type of atom, characterized by its particular number of protons in the nuclei of its atoms, known as the atomic number and represented by the symbol Z. The mass number is the sum of the number of protons and neutrons in a nucleus. Although all the nuclei of all atoms belonging to one element will have the same atomic number, they may not necessarily have the same mass number; atoms of an element which have different mass numbers are known as isotopes. For example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, but atoms of carbon may have mass numbers of 12 or 13.[41]
The standard presentation of the chemical elements is in the periodic table, which orders elements by atomic number. The periodic table is arranged in groups, or columns, and periods, or rows. The periodic table is useful in identifying periodic trends.[42]
A compound is a pure chemical substance composed of more than one element. The properties of a compound bear little similarity to those of its elements.[43] The standard nomenclature of compounds is set by the International Union of Pure and Applied Chemistry (IUPAC). Organic compounds are named according to the organic nomenclature system.[44] Inorganic compounds are named according to the inorganic nomenclature system.[45] In addition the Chemical Abstracts Service has devised a method to index chemical substances. In this scheme each chemical substance is identifiable by a number known as its CAS registry number.
A molecule is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. However, this definition only works well for substances that are composed of molecules, which is not true of many substances (see below). Molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs.
Thus, molecules exist as electrically neutral units, unlike ions. When this rule is broken, giving the "molecule" a charge, the result is sometimes named a molecular ion or a polyatomic ion. However, the discrete and separate nature of the molecular concept usually requires that molecular ions be present only in well-separated form, such as a directed beam in a vacuum in a mass spectrograph. Charged polyatomic collections residing in solids (for example, common sulfate or nitrate ions) are generally not considered "molecules" in chemistry.
The "inert" or noble gas elements (helium, neon, argon, krypton, xenon and radon) are composed of lone atoms as their smallest discrete unit, but the other isolated chemical elements consist of either molecules or networks of atoms bonded to each other in some way. Identifiable molecules compose familiar substances such as water, air, and many organic compounds like alcohol, sugar, gasoline, and the various pharmaceuticals.
However, not all substances or chemical compounds consist of discrete molecules, and indeed most of the solid substances that makes up the solid crust, mantle, and core of the Earth are chemical compounds without molecules. These other types of substances, such as ionic compounds and network solids, are organized in such a way as to lack the existence of identifiable molecules per se. Instead, these substances are discussed in terms of formula units or unit cells as the smallest repeating structure within the substance. Examples of such substances are mineral salts (such as table salt), solids like carbon and diamond, metals, and familiar silica and silicate minerals such as quartz and granite.
One of the main characteristics of a molecule is its geometry often called its structure. While the structure of diatomic, triatomic or tetra atomic molecules may be trivial, (linear, angular pyramidal etc.) the structure of polyatomic molecules, that are constituted of more than six atoms (of several elements) can be crucial for its chemical nature.
| Examples of pure chemical substances. From left to right: the elements tin (Sn) and sulfur (S), diamond (an allotrope of carbon), sucrose (pure sugar), and sodium chloride (salt) and sodium bicarbonate (baking soda), which are both ionic compounds. |
A chemical substance is a kind of matter with a definite composition and set of properties.[46] A collection of substances is called a mixture. Examples of mixtures are air and alloys.[citation needed]
The mole is a unit of measurement that denotes an amount of substance (also called chemical amount). The mole is defined as the number of atoms found in exactly 0.012 kilogram (or 12 grams) of carbon-12, where the carbon-12 atoms are unbound, at rest and in their ground state.[47] The number of entities per mole is known as the Avogadro constant, and is determined empirically to be approximately 6.022×1023 mol−1.[48] Molar concentration is the amount of a particular substance per volume of solution, and is commonly reported in moldm-3.[49]
In addition to the specific chemical properties that distinguish different chemical classifications chemicals can exist in several phases. For the most part, the chemical classifications are independent of these bulk phase classifications; however, some more exotic phases are incompatible with certain chemical properties. A phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature.
Physical properties, such as density and refractive index tend to fall within values characteristic of the phase. The phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions.
Sometimes the distinction between phases can be continuous instead of having a discrete boundary, in this case the matter is considered to be in a supercritical state. When three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions.
The most familiar examples of phases are solids, liquids, and gases. Many substances exhibit multiple solid phases. For example, there are three phases of solid iron (alpha, gamma, and delta) that vary based on temperature and pressure. A principal difference between solid phases is the crystal structure, or arrangement, of the atoms. Another phase commonly encountered in the study of chemistry is the aqueous phase, which is the state of substances dissolved in aqueous solution (that is, in water).
Less familiar phases include plasmas, Bose-Einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. While most familiar phases deal with three-dimensional systems, it is also possible to define analogs in two-dimensional systems, which has received attention for its relevance to systems in biology.
Atoms sticking together in molecules or crystals are said to be bonded with one another. A chemical bond may be visualized as the multipole balance between the positive charges in the nuclei and the negative charges oscillating about them.[50] More than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom.
A chemical bond can be a covalent bond, an ionic bond, a hydrogen bond or just because of Van der Waals force. Each of these kinds of bonds is ascribed to some potential. These potentials create the interactions which hold atoms together in molecules or crystals. In many simple compounds, Valence Bond Theory, the Valence Shell Electron Pair Repulsion model (VSEPR), and the concept of oxidation number can be used to explain molecular structure and composition.
An ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non-metal atom, becoming a negatively charged anion. The two oppositely charged ions attract one another, and the ionic bond is the electrostatic force of attraction between them. For example, sodium (Na), a metal, loses one electron to become an Na+ cation while chlorine (Cl), a non-metal, gains this electron to become Cl-. The ions are held together due to electrostatic attraction, and that compound sodium chloride (NaCl), or common table salt, is formed.
In a covalent bond, one or more pairs of valence electrons are shared by two atoms: the resulting electrically neutral group of bonded atoms is termed a molecule. Atoms will share valence electrons in such a way as to create a noble gas electron configuration (eight electrons in their outermost shell) for each atom. Atoms that tend to combine in such a way that they each have eight electrons in their valence shell are said to follow the octet rule. However, some elements like hydrogen and lithium need only two electron in their outermost shell to attain this stable configuration; these atoms are said to follow the duet rule, and in this way they are reaching the electron configuration of the noble gas helium, which has two electrons in its outer shell.
Similarly, theories from classical physics can be used to predict many ionic structures. With more complicated compounds, such as metal complexes, valence bond theory is less applicable and alternative approaches, such as the molecular orbital theory, are generally used. See diagram on electronic orbitals.
In the context of chemistry, energy is an attribute of a substance as a consequence of its atomic, molecular or aggregate structure. Since a chemical transformation is accompanied by a change in one or more of these kinds of structures, it is invariably accompanied by an increase or decrease of energy of the substances involved. Some energy is transferred between the surroundings and the reactants of the reaction in the form of heat or light; thus the products of a reaction may have more or less energy than the reactants.
A reaction is said to be exergonic if the final state is lower on the energy scale than the initial state; in the case of endergonic reactions the situation is the reverse. A reaction is said to be exothermic if the reaction releases heat to the surroundings; in the case of endothermic reactions, the reaction absorbs heat from the surroundings.
Chemical reactions are invariably not possible unless the reactants surmount an energy barrier known as the activation energy. The speed of a chemical reaction (at given temperature T) is related to the activation energy E, by the Boltzmann's population factor - that is the probability of a molecule to have energy greater than or equal to E at the given temperature T. This exponential dependence of a reaction rate on temperature is known as the Arrhenius equation. The activation energy necessary for a chemical reaction to occur can be in the form of heat, light, electricity or mechanical force in the form of ultrasound.[51]
A related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. A reaction is feasible only if the total change in the Gibbs free energy is negative, ; if it is equal to zero the chemical reaction is said to be at equilibrium.
There exist only limited possible states of energy for electrons, atoms and molecules. These are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. The atoms/molecules in a higher energy state are said to be excited. The molecules/atoms of substance in an excited energy state are often much more reactive; that is, more amenable to chemical reactions.
The phase of a substance is invariably determined by its energy and the energy of its surroundings. When the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water (H2O); a liquid at room temperature because its molecules are bound by hydrogen bonds.[52] Whereas hydrogen sulfide (H2S) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole-dipole interactions.
The transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. However, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. Thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. For example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy.
The existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. Different kinds of spectra are often used in chemical spectroscopy, e.g. IR, microwave, NMR, ESR, etc. Spectroscopy is also used to identify the composition of remote objects - like stars and distant galaxies - by analyzing their radiation spectra.
The term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances.
When a chemical substance is transformed as a result of its interaction with another substance or with energy, a chemical reaction is said to have occurred. A chemical reaction is therefore a concept related to the 'reaction' of a substance when it comes in close contact with another, whether as a mixture or a solution; exposure to some form of energy, or both. It results in some energy exchange between the constituents of the reaction as well with the system environment which may be designed vessels which are often laboratory glassware.
Chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more smaller molecules, or rearrangement of atoms within or across molecules. Chemical reactions usually involve the making or breaking of chemical bonds. Oxidation, reduction, dissociation, acid-base neutralization and molecular rearrangement are some of the commonly used kinds of chemical reactions.
A chemical reaction can be symbolically depicted through a chemical equation. While in a non-nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for a nuclear reaction this holds true only for the nuclear particles viz. protons and neutrons.[53]
The sequence of steps in which the reorganization of chemical bonds may be taking place in the course of a chemical reaction is called its mechanism. A chemical reaction can be envisioned to take place in a number of steps, each of which may have a different speed. Many reaction intermediates with variable stability can thus be envisaged during the course of a reaction. Reaction mechanisms are proposed to explain the kinetics and the relative product mix of a reaction. Many physical chemists specialize in exploring and proposing the mechanisms of various chemical reactions. Several empirical rules, like the Woodward-Hoffmann rules often come handy while proposing a mechanism for a chemical reaction.
According to the IUPAC gold book a chemical reaction is "a process that results in the interconversion of chemical species."[54] Accordingly, a chemical reaction may be an elementary reaction or a stepwise reaction. An additional caveat is made, in that this definition includes cases where the interconversion of conformers is experimentally observable. Such detectable chemical reactions normally involve sets of molecular entities as indicated by this definition, but it is often conceptually convenient to use the term also for changes involving single molecular entities (i.e. 'microscopic chemical events').
An ion is a charged species, an atom or a molecule, that has lost or gained one or more electrons. When an atom loses an electron and thus has more protons than electrons, the atom is a positively-charged ion or cation. When an atom gains an electron and thus has more electrons than protons, the atom is a negatively-charged ion or anion. Cations and anions can form a crystalline lattice of neutral salts, such as the Na+ and Cl- ions forming sodium chloride, or NaCl. Examples of polyatomic ions that do not split up during acid-base reactions are hydroxide (OH−) and phosphate (PO43−).
Plasma is composed of gaseous matter that has been completely ionized, usually through high temperature.
A substance can often be classified as an acid or a base. There are several different theories which explain acid-base behavior. The simplest is Arrhenius theory, which states than an acid is a substance that produces hydronium ions when it is dissolved in water, and a base is one that produces hydroxide ions when dissolved in water. According to Brønsted–Lowry acid–base theory, acids are substances that donate a positive hydrogen ion to another substance in a chemical reaction; by extension, a base is the substance which receives that hydrogen ion.
A third common theory is Lewis acid-base theory, which is based on the formation of new chemical bonds. Lewis theory explains that an acid is a substance which is capable of accepting a pair of electrons from another substance during the process of bond formation, while a base is a substance which can provide a pair of electrons to form a new bond. According to this theory, the crucial things being exchanged are charges.[55][unreliable source?] There are several other ways in which a substance may be classified as an acid or a base, as is evident in the history of this concept [56]
Acid strength is commonly measured by two methods. One measurement, based on the Arrhenius definition of acidity, is pH, which is a measurement of the hydronium ion concentration in a solution, as expressed on a negative logarithmic scale. Thus, solutions that have a low pH have a high hydronium ion concentration, and can be said to be more acidic. The other measurement, based on the Brønsted–Lowry definition, is the acid dissociation constant (Ka), which measure the relative ability of a substance to act as an acid under the Brønsted–Lowry definition of an acid. That is, substances with a higher Ka are more likely to donate hydrogen ions in chemical reactions than those with lower Ka values.
Redox (reduction-oxidation) reactions include all chemical reactions in which atoms have their oxidation state changed by either gaining electrons (reduction) or losing electrons (oxidation). Substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. An oxidant removes electrons from another substance. Similarly, substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers.
A reductant transfers electrons to another substance, and is thus oxidized itself. And because it "donates" electrons it is also called an electron donor. Oxidation and reduction properly refer to a change in oxidation number—the actual transfer of electrons may never occur. Thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number.
Although the concept of equilibrium is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible. For example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more than one kind of phase.
A system of chemical substances at equilibrium, even though having an unchanging composition, is most often not static; molecules of the substances continue to react with one another thus giving rise to a dynamic equilibrium. Thus the concept describes the state in which the parameters such as chemical composition remain unchanged over time.
Chemical reactions are governed by certain laws, which have become fundamental concepts in chemistry. Some of them are:
Chemistry is typically divided into several major sub-disciplines. There are also several main cross-disciplinary and more specialized fields of chemistry.[57]
Other disciplines within chemistry are traditionally grouped by the type of matter being studied or the kind of study. These include inorganic chemistry, the study of inorganic matter; organic chemistry, the study of organic (carbon based) matter; biochemistry, the study of substances found in biological organisms; physical chemistry, the study of chemical processes using physical concepts such as thermodynamics and quantum mechanics; and analytical chemistry, the analysis of material samples to gain an understanding of their chemical composition and structure. Many more specialized disciplines have emerged in recent years, e.g. neurochemistry the chemical study of the nervous system (see subdisciplines).
Other fields include agrochemistry, astrochemistry (and cosmochemistry), atmospheric chemistry, chemical engineering, chemical biology, chemo-informatics, electrochemistry, environmental chemistry, femtochemistry, flavor chemistry, flow chemistry, geochemistry, green chemistry, histochemistry, history of chemistry, hydrogenation chemistry, immunochemistry, marine chemistry, materials science, mathematical chemistry, mechanochemistry, medicinal chemistry, molecular biology, molecular mechanics, nanotechnology, natural product chemistry, oenology, organometallic chemistry, petrochemistry, pharmacology, photochemistry, physical organic chemistry, phytochemistry, polymer chemistry, radiochemistry, solid-state chemistry, sonochemistry, supramolecular chemistry, surface chemistry, synthetic chemistry, thermochemistry, and many others.
The chemical industry represents an important economic activity. The global top 50 chemical producers in 2004 had sales of 587 billion US dollars with a profit margin of 8.1% and research and development spending of 2.1% of total chemical sales.[59]
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