Question

Which among the following species have the same number of electrons in its outermost as well as penultimate shell?

• A. $Mg^{2+}$
• B. $O^{2-}$
• C. $F^{-}$
• D. $Ca^{2+}$

Answer 1

Answer: (D)

$Ca^{2+}$

Answer 2

${ }_{20} Ca =2,8,8,2 Ca ^{2+}=2,8,8$ Hence, $Ca ^{2+}$ has $8$ electrons each in outermost and penultimate shell.