Question

which of the following best represents a pair of isotopes?
carbon - 12 and carbon - 14
carbon - 12 and oxygen - 12
carbon - 12 and $\frac{24}{14}mg$
$\frac{6}{12}c$ and $\frac{12}{6}c$

Explanation:

Isotopes are atoms of the same element with different mass - numbers due to different numbers of neutrons. Carbon - 12 and Carbon - 14 are both carbon atoms with mass numbers 12 and 14 respectively. Different elements like carbon and oxygen cannot be isotopes of each other. Also, the notation in the last option is incorrect for representing isotopes.

Answer:

Carbon-12 and Carbon-14