第6章分子结构和共价键理论
第6章 分子结构和共价键理论
6.1Lewis Electron-dot Diagrams同种元素的原子一单质分子？电负性相近元素的原子一→稳定的分子？年，美，G.N.1916Lewis提出了共价键(Covalent bond)理论。过共价键：分子中原子间通共用电子对结合而形成的化学键(1875~1946)八隅体规则
6.1 Lewis Electron-dot Diagrams 同种元素的原子→单质分子? 电负性相近元素的原子→稳定的分子? 1916 年 ， 美 ， G. N. Lewis 提 出 了 共 价 键 (Covalent bond)理论。 共价键：分子中原子间通 过 共用电子对结合而 形成的化学键 八隅体规则 (1875~1946)
Gilbert Newton Lewis FormemRS (October25 (or 23), 1875 - March 23. 1946) was anAmerican physical chemist known for thediscovery of the covalent bond and his conceptof electron pairs; his Lewis dot structures andother contributions to valence bond theoryhave shaped modern theories of chemicalbonding.Lewis successfully contributed tothermodynamics, photochemistry, and isotope separation, and isalso known for his concept of acids and bases.G. N. Lewis was born in Weymouth, Massachusetts. Afterreceiving his PhD in chemistry from Harvard University andstudying abroad in Germany and the Philippines, Lewis movedto California to teach chemistry at the University of California.BerkeleyThough he was nominated 41 times, G. N. Lewis never won theNobel Prize in Chemistry. hydrogen cyanide, suicide
Gilbert Newton Lewis FormemRS (October 25 (or 23), 1875 – March 23, 1946) was an American physical chemist known for the discovery of the covalent bond and his concept of electron pairs; his Lewis dot structures and other contributions to valence bond theory have shaped modern theories of chemical bonding. Lewis successfully contributed to thermodynamics, photochemistry, and isotope separation, and is also known for his concept of acids and bases. G. N. Lewis was born in Weymouth, Massachusetts. After receiving his PhD in chemistry from Harvard University and studying abroad in Germany and the Philippines, Lewis moved to California to teach chemistry at the University of California, Berkeley. Though he was nominated 41 times, G. N. Lewis never won the Nobel Prize in Chemistry. hydrogen cyanide, suicide
6.1 Lewis Electron-dot Diagrams成功：解释了由相同原子组成的分子（H、O,等）以及性质相近的不同原子组成的分子（HCI、H,O等），并揭示了共价键和离子键的区别。局限：1）某些分子的中心原子最外层电子数不是稀有气体结构；但仍能稳定存在；如，BF3；SFs；PCls;2）不能解释共价键的特性（方向性、饱和性等）；3）不能解释单电子键H+和O的磁性：4）不能阐明电子共用的本质
局限： 1）某些分子的中心原子最外层电子数不是稀有气体结构； 但仍能稳定存在；如，BF3；SF6；PCl5； 2）不能解释共价键的特性（方向性、饱和性等）； 3）不能解释单电子键H2 + 和 O2 的磁性； 4）不能阐明电子共用的本质。 成功： 解释了由相同原子组成的分子（H2、O2等）以及性质 相近的不同原子组成的分子（HCl、H2O等），并揭示了共 价键和离子键的区别。 6.1 Lewis Electron-dot Diagrams
价键理论6.2，VBT)(valence bond theory,1927年，Heitler和London用量子力学处理氢气分子H2，解决氢原子间化学键的本质问题后经Pauling等人发展建立了现代价键理论也称为电子配对法（VB法）。1.共价键的形成和本质组成分子的两原子的未成对电子自旋相反，成对偶合形成共价键。与Lewis法不同
1927 年，Heitler 和 London 用量子力学处理氢 气分子H2，解决氢原子间化学键的本质问题。 后经Pauling等人发展建立了现代价键理论也称为 电子配对法（VB 法）。 6.2 价键理论（valence bond theory，VBT） 1. 共价键的形成和本质 组成分子的两原子的未成对电子自旋相反，成对 偶合形成共价键。 与Lewis法不同