When an Element Has 12 Neutrons and a Z=12, What ${ }_{12}^{24} \mathrm{Mg}$

Multiple Choice

When an element has 12 neutrons and a Z=12, what element and isotope are present?

A) ${ }_{12}^{24} \mathrm{Mg}$
B) ${ }_{12}^{12} \mathrm{Mg}$
C) ${ }_{24}^{24} \mathrm{Mg}$
D) ${ }_{24}^{24} \mathrm{Cr}$