O^2-, F^–, Na⁺ and Mg²⁺ are called as __________

O^2-, F^–, Na^+, and Mg²⁺ are known as isoelectronic species as they all have the same no. of electrons (10).

 Isotopes contain the same no. of protons but a different number of neutrons. Isobars have the same mass number but a different atomic number.