Question

what is the mass number of an atom containing 12 protons and 13 neutrons?
a) 25
b) 12
c) 12.5
d) 13

Explanation:

Step1: Recall the formula for mass number

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

Step2: Substitute the given values

Here, \(p = 12\) and \(n=13\). So, \(A=12 + 13\).

Step3: Calculate the sum

\(12+13 = 25\).

Answer:

A. 25