Question

If an element has 4 protons and 5 neutrons its mass number is

Answer 1

its atomic mass will equal up to 9

Answer 2

9

Explanation:

The mass number (A) is the sum of the number of protons (p) and the number of neutrons (n).

A = p + n

p = 4

n = 5 Calculate A

A = 4 + 5

A = 9