The mass number of the atom is 45.
Given:
An atom contains 21 electrons, 21 protons, and 24 neutrons.
To find:
The mass number of an atom.
Solution:
Number of protons in atom = p = 21
Number of neutrons in atom = n = 24
Mass number of an atom = A
[tex]A = p + n \\\\A = 21 + 24 \\\\A = 45[/tex]
The mass number of the atom is 45.
Learn more about mass number here:
brainly.com/question/1371394?referrer=searchResults
