Mass number
The mass number refers to the nucleons in the atom's nucleus. This topic is part of Atomic Structure within Science & Nature. This page currently draws on 4 supporting questions, with answers and bonus facts available below.
Mass number trivia questions
What does an atom's mass number count?
Answer: Protons plus neutrons
Bonus fact: The mass number refers to the nucleons in the atom's nucleus.
How is mass number usually written in isotope notation?
Answer: As a whole number associated with the element symbol
Bonus fact: Carbon-14, for example, has a mass number of 14.
Two isotopes of the same element have the same number of protons but different numbers of what?
Answer: Neutrons
Bonus fact: Changing neutron count changes the mass number without changing the element's identity.
Isotopes are atoms of the same element with different numbers of what?
Answer: Neutrons
Bonus fact: They have the same atomic number but different mass numbers.