Question

Explain why a ferrous cation is smaller than oxygen anion ?

general explanation:

1.) Cation is formed due to loss of electron. So, it’s no of shells decrease and atomic size get reduce.

2.) Anion is formed due to gain of electrons. So, after gaining the electrons repulsion between electron increases and atomic size increases. So, repulsion between electrons is main reason of large size of anion

I need the specific answer in terms of ferrous cation and oxygen anion?

Answer 1

As oxygen anion is formed by gain of 2 elecctrons,the electron-electron repulsion increases the size of O2- ,the electronic configuration of O atom is-

, after acccepting 2electrons in the outermost shell, it attains the configuration of neon core making the aomic radius of r()=152 pm

whereas Fe2+.removing 2 electrons from its outermost shell,has more no of protons than the electrons,so the electron cloud is more closer to the nucleus than 'Fe' atom making the ionic radius of Fe2+=70pm.