The mass number of the nucleus is
A)4.
B)5.
C)9.
D)13.

Question

The mass number of the nucleus  is
A)4. 
B)5. 
C)9. 
D)13.

Quizplus · Accepted Answer

The mass number of a nucleus is equal to the sum of protons and neutrons in its nucleus. From the given symbol, we can determine the atomic number of the nucleus to be 5 (the subscript, denoted by the number of protons). Therefore, to get the mass number, we add the number of protons (5) to the number of neutrons. Since the mass number is not given, we look for an answer choice where the sum of 5 and the number of neutrons is provided. The only answer choice that satisfies this is C, where the number of neutrons is 4. Therefore, the mass number of the nucleus is 9 (5 protons + 4 neutrons = 9).

The Mass Number of the Nucleus Is