Question

what is the mass number of a carbon atom which has six protons and six neutrons.
a 72
b 18
c 6
d 12

Explanation:

Step1: Recall mass - number formula

The mass number ($A$) of an atom is the sum of the number of protons ($p$) and neutrons ($n$), i.e., $A=p + n$.

Step2: Substitute given values

Given that $p = 6$ and $n=6$, then $A=6 + 6=12$.

Answer:

d. 12