Total number of ions from the following with noble gas configuration is Sr 2 + ( Z = 38 ) , Cs + ( Z = 55 ) , La 2 + ( Z = 57 ) Pb 2 + ( Z = 82 ) , Yb 2 + ( Z = 70 ) and Fe 2 + ( Z = 26 )

Step-by-step solution

Noble gas configuration = ns 2 np 6 38 Sr 2 + = [ 36 Kr ] Cs + = [ 54 Xe ] Yb 70 2 + = [ 54 Xe ] 4 f 14 57 La 2 + = [ 54 Xe ] 5 d 1 82 Pb 2 + = [ 54 Xe ] 4 f 14 5 d 10 6 s 2 26 Fe 2 + = [ 18 Ar ] 3 d 6 Cs + and Sr 2 + have noble gas configuration, which are Xe and Kr , respectively. Hence, the answer is 2 .