In periodic table Li,Na,Mg,Be are present in following ways :-
Group 1
Group 2
Li
Be
Na
Mg
Note: (1) In periodic table from left to right the size of element decreases. (2) In periodic table, from top to bottom size of element increases. So, Be+2 will be the smallest in size. Among Li+and Na+, size of Na+>Li+and among Be+2 and Mg+2, size of Mg+2>Be+2 So, the correct order will be, Na+>Li+>Mg+2>Be+2