Be²+ is Isoelectronic with which of the following ions . (a)Li2+ (b)Na+ (c)Mg²+ (d)H+

Hi,

i think your question is incorrect as none of the options are right.

This question appeared in AIPMT.

AND THE FIRST OPTION WAS Li+ not 2+

HENCE, Be2+ is isoelectronic with Li+. 

be2+ (atomic number 4...loses two electrons...effective 2)

li+ (atomic number 3...loses one electron..effective 2)

@ manisha 
your  options are incorrect . 
what u need to understand is that isoelectronic means that they both have to contain same no of electrons . 
so, if u will calculate be 2+ (the effective electrons is 2 ) 
then it will be isoelectronic with only LI+ . BUT AS the option contains li 2+ then that will not be correct 
and none of the other option satisfy the criterion of same electrons with be 2+ 
HOPE IT HELPS 
in case of other doubts do feel free to post on the forum .