水的密度在4℃时最大,而不是在熔点温度时。水究竟为什么会有这样特殊的性质呢?这完全是由水分子的特殊结构引起的。气态水分子键角为104°52’′,由于氧为 sp~3杂化,有两对孤对电子,而氢原子显正电性,这样就形成了四面体取向的电荷分布,水分子就按这四个方向以四面体取向由氢键相连,构成了一个空旷的框架结构,但由于氢键键能为21 kJ·mol~(-1)远小于正常共价键(几百千焦每摩尔),所以这种框架结构很易破碎。 The density of water at 4 ℃ maximum, rather than at the melting temperature. Why water has such a special nature? This is entirely caused by the special structure of water molecules. The molecular bond angle of gaseous water molecules is 104 ° 52 ". Since the oxygen is sp ~ 3 hybridized, there are two pairs of lone pairs of electrons, and the hydrogen atoms are positively charged, thus forming a tetrahedral oriented charge distribution. The water molecules According to these four directions, tetrahedral orientations are connected by hydrogen bonds, forming an open frame structure. However, since the hydrogen bond energy is 21 kJ · mol -1, it is much smaller than the normal covalent bond Moore), so this frame structure is very fragile.