Ca2+ is isoelectronic with
a- Mg2-
b-Kr-
c-Ar
d-Na+
The correct answer is (c). Isoelectronic means species having same number of electrons. Ca2+ has 18 electrons and Ar also has 18 electrons.
Ca2+ is isoelectronic with
a- Mg2-
b-Kr-
c-Ar
d-Na+