Answer:
B. 14
Explanation:
For an element:
- Atomic number: is the number of protons in the nucleus (p)
- Mass number: it is the number of protons (p) + neutrons (n) in the nucleus
For Al (aluminium), we have:
p = 13
p + n = 27
Substituting the first equation into the second one, we find the number of neutrons:
n = 27 - p = 27 - 13 = 14
