Question

what is the mass number of a carbon isotope that has seven neutrons? carbon has six protons. a 7 b 13 c 12 d 4

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: Identify number of protons and neutrons

Given that the number of protons in carbon $p = 6$ and the number of neutrons $n=7$.

Step3: Calculate mass number

$A=6 + 7=13$.

Answer:

B. 13