An Isotope with 22 Neutrons and 18 Protons Is What ${ }_{18}^{42} \mathrm{Ar}$

Multiple Choice

An isotope with 22 neutrons and 18 protons is what?

A) ${ }_{18}^{42} \mathrm{Ar}$
B) ${ }_{18}^{22} \mathrm{Ar}$
C) ${ }_{18}^{40} \mathrm{Ar}$
D) ${ }_{22}^{18} \mathrm{Ar}$