The charge/size ratio of a cation determines its polarizing power. Which one of the following sequences represents

Q. The charge/size ratio of a cation determines its polarizing power. Which one of the following sequences represents the increasing order of the polarizing order of the polarizing power of the cationic species, K⁺, Ca⁺⁺, Mg2⁺, Be2⁺?

1. Ca2+ < Mg2+ < Be+ < K+
2. Mg2+ < Be2+ < K+ < Ca2+
3. Be2+ < K+ < Ca2+ < Mg2+
4. K+ < Ca2+ < Mg2+ < Be2+

Answer: K+ < Ca2+ < Mg2+ < Be2+