Be2+ is isoelectronic with which of the following ions?
- H+
- Li+
- Na+
- Mg2+
Answer
(2) Li+
Solution
Number of electrons: Be2+ = 4 − 2 = 2.
H+ = 0, Li+ = 3 − 1 = 2, Na+ = 11 − 1 = 10, Mg2+ = 12 − 2 = 10.
∴ Be2+ and Li+ both have 2 electrons, so they are isoelectronic.
Answer: (2)