”每一个电子层不分隔开来“以下例子中最后一步,为什么写了这句话之后就把s和d的互换位置如24号元素铬的24个核外电子依次排列为1s22s22p63s23p64s23d4根据洪特规则,d亚层处于半充满时较为

Question

”每一个电子层不分隔开来 “ 以下例子中最后一步,为什么写了这句话之后就把s和d的互换位置
如24号元素铬的24个核外电子依次排列为
1s22s22p63s23p64s23d4
根据洪特规则,d亚层处于半充满时较为稳定,故其排布式应为：
1s22s22p63s23p64s13d5
最后,按照人们的习惯“每一个电子层不分隔开来”,改写成
1s22s22p63s23p63d54s1

Answer 1

In this case,the energy of 4s shell is lower than that of 3d shell,that's why you arranged them in the order you mentioned and you filled in electrons to 4s shell first.But since 3d is still belong to the n=3 shell,after filling electrons,you can rearrange in order to put all shells with the same principal quantum number together.