Give the symbol for:

a. the cation possessing a positive one charge that is isoelectronic with argon.

b. the anion possessing a negative two charge that is isoelectronic with krypton.

a. K⁺

b. Se²⁻

Explanation:

Isoelectronic species are those that have the same number of electrons.

a.

Ar has 18 electrons. K has 19 electrons, so when it loses 1 electron to form K⁺, it is isoelectronic with Ar.

b.

Kr has 36 electrons. Se has 34 electrons, so when it gains 2 electrons to form Se²⁻, it is isoelectronic with Kr.