Helm Lothar, Merbach André E
Institute of Chemical Sciences and Engineering ISIC, EPFL, Station 6, CH-1015 Lausanne;, Email:
Institute of Chemical Sciences and Engineering ISIC, EPFL, Station 6, CH-1015 Lausanne.
Chimia (Aarau). 2019 Mar 27;73(3):179-184. doi: 10.2533/chimia.2019.179.
Mendeleev in his first publication ordered the chemical elements following an apparent periodicity of properties such as atomic volume and valence. The reactivity of the elements was only studied systematically many years later. To illustrate the systematic variation of kinetics across the periodic table we compare water residence times for monoatomic ions in aqueous solution. A tremendous variation of τ by over 20 orders of magnitude is found, ranging from ~10 ps to about 200 years. Apart from some small +2 and +3 cations, all main group elements have very short residence times <10 ns. Transition metal cations of the d-block have water residence times that depend on the electronic configuration. τ of lanthanide ions are surprisingly short with values of 10 ns and shorter. This is due to an equilibrium between 8 and 9 coordinated ions leading to a low energy of the transition state for the water exchange reaction.
门捷列夫在其首次发表的论文中，按照原子体积和化合价等明显的性质周期性对化学元素进行了排序。元素的反应活性直到多年后才得到系统研究。为了说明动力学在元素周期表中的系统变化，我们比较了水溶液中单原子离子的水停留时间。发现τ有超过20个数量级的巨大变化，范围从约10皮秒到约200年。除了一些小的+2和+3阳离子外，所有主族元素的停留时间都非常短，小于10纳秒。d区过渡金属阳离子的水停留时间取决于电子构型。镧系离子的τ出奇地短，值为10纳秒及更短。这是由于8配位和9配位离子之间的平衡导致水交换反应的过渡态能量较低。
