Which of the following sets contain only isoelectronic ions?

Options

A. `Zn^(+), Ca^(2+), Ga^(2+), Al^(3+)`
B. `K^(+), Ca^(2+), Sc^(3+), Cl^(-)`
C. `P^(3-), S^(2-), Cl^(-), K^(+)`
D. `Ti^(4+), Ar, Cr^(3-), V^(5+)`

Answer

B, C

Explanation

(b,c)
a) `Zn^(2+) (30-2=28), Ca^(2+)(20-2=18), Ga^(3+)(31-3=28), Al^(3+)(13-3=10)`
These species have different number of electrons and hence are not isoelectrons ions.
b) `K^(+)(19-1=18), Ca^(2+)(20-2=18), Sc^(3+)(21-3=18),Cl^(-)(17+1=18)`
These are all isoelectronic ions since each one of them has 18 electrons.
C) `P^(3-)(15+3=18), S^(2-)(16+2=18), Cl^(-)(17+1=18), K^9+) (19-1=18)`
These are all isoelectronic ions since each one fo them has 18 electrons.
d) `Ti^(4+)(22-4=18), Ar(18), Cr^(3+)(24-3=21), V^(5+)(23-5=18)`
These have different number of electrons and hence are not isoelectronic ions.