According to the periodic table, which of the following indicates the correct decreasing order of ionization energy?

Question

Cs > Li > Na > K 

Li > Na > Cs > K

Li > Na > K > Cs

Li > Cs > Na > K 

Answer 1

Ionization energy decreases going down within a group of elements. Looking at the periodic table, the elements being considered here are all in group 1 (alkali metals). So, in decreasing order of IE, we would have...

Li > Na > K > Cs