…The theory of covalent bonds in hydrogen molecules was first quantitatively established by W. Heitler and F. London (1927), and was further expanded by John Clarke Slater (1900-76) and LC Pauling, and systematized as the valence bond theory. This is still used as a useful method today, but around the same time, Friedlich Hund (1896- ), Robert Sanderson Mulliken (1896-1986), and Erich Armand Arthur Joseph Hückel (1896-1980) developed the molecular orbital theory, which is a quantum theory of valence. The molecular orbital theory was initially an empirical method that only dealt with π electrons, like the Hückel method, and considered the necessary energy integral values as empirical parameters. … From [The Rules of Hund]…In a single electron configuration, the orbital energy of each electron is constant, but depending on the interactions between the electrons, the overall energy of the atom can be high or low. In 1925, Friedrich Hund of Germany discovered the following two regular phenomena regarding the ground state of an atom (the state with the lowest energy) from experimental data on atomic spectra: (1) In the lowest-energy electron configuration, the state in which the combined spin of the electrons is at its maximum is the ground state of the atom. … *Some of the terminology that mentions "Hund, F." is listed below. Source | Heibonsha World Encyclopedia 2nd Edition | Information |
…水素分子の共有結合の理論はW.ハイトラーとF.ロンドンによって初めて定量的基礎が与えられ(1927),さらにスレーターJohn Clarke Slater(1900‐76),L.C.ポーリングによって拡張され,原子価結合法として体系化された。これは今日でもなお有用な手法として利用されているが,一方同じころ,フントFriedlich Hund(1896‐ ),マリケンRobert Sanderson Mulliken(1896‐1986),ヒュッケルErich Armand Arthur Joseph Hückel(1896‐1980)らによって,原子価の量子論である分子軌道法が展開された。分子軌道法は初めはヒュッケル法のようにπ電子だけを扱い,必要なエネルギー積分の値を経験的パラメーターとみなす経験的方法であった。… 【フントの規則】より…一つの電子配置においては,個々の電子の軌道運動のエネルギーは一定であるが,電子間の相互関係によって,原子全体のエネルギーは高い状態になることもあり,低い状態になることもある。ドイツのフントFriedrich Hundは,1925年に原子の基底状態(もっともエネルギーの低い状態)について,原子スペクトルの実験データから,次の2項目の規則的現象を見いだした。すなわち,(1)もっともエネルギーの低い電子配置において,電子の合成スピンが最大の状態が原子の基底状態である。… ※「Hund,F.」について言及している用語解説の一部を掲載しています。 出典|株式会社平凡社世界大百科事典 第2版について | 情報 |
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