The mass number of an atom is determined primarily by the _______ it contains.

Question

Quizplus · Accepted Answer

The mass number of an atom is defined as the sum of the number of protons and the number of neutrons in the nucleus of an atom. Therefore, the correct answer is D- sum of number of protons and neutrons. The number of electrons in an atom does not contribute to the mass number since their mass is negligible. The sum of the number of protons and electrons gives the atomic number, which identifies the element. The number of charges on an atom tells us about its ionization state and not about its mass number. Therefore, option D is the correct answer.

The Mass Number of an Atom Is Determined Primarily by the _______