Question

`Be^(2+)` is isoelectronic with which of the following ions ?
A. `H^+`
B. `Li^+`
C. `Na^+`
D. `Mg^(2+)`

Answer 1

Correct Answer - B
Isoelectronic species contain same number of electrons. `Be^(2+)` contains 2 electrons .Among the given options, only `Li^+` contains 2 electrons and therefore, it is isoelectronic with `Be^(2+)`.
`H^(+)to` no electron , `Na^(+) to 10 e^(-)`
`Li^(+) to 2 e^(-)`
Hence, `Be^(2+)` is isoelectronic with `Li^+`