Question

Which of the following species has more number of electrons than its neutrons?
[Given: mass number, $C=12;O=16;F=19;Mg=24$]

• A. $C$
• B. $O^{2-}$
• C. $F^{-}$
• D. $M{g}^{2+}$

Answer 1

The correct option is B $O^{2-}$

${}_6^{12}C$ has
$\text{number of protons},p=6$
$\text{number of electrons},e=6$
$\text{number of neutrons},n=6$

${}_8^{16}{O}^{2-}$ has
$\text{number of protons},p=8$
$\text{number of electrons},e=10$
$\text{number of neutrons},n=8$

${}_9^{19}{F}^{-}$ has
$\text{number of protons},p=9$
$\text{number of electrons},e=10$
$\text{number of neutrons},n=10$

${}_{12}^{24}M{g}^{2+}$ has
$\text{number of protons},p=12$
$\text{number of electrons},e=10$
$\text{number of electrons},en=12$