mass number

noun

, Physics.

1. the integer nearest in value to the atomic weight of an atom and equal to the number of nucleons in the nucleus of the atom. : A

mass number

noun

1. the total number of neutrons and protons in the nucleus of a particular atom A Also callednucleon number

mass number

1. The total number of protons and neutrons in the nucleus of an atom. For example, nitrogen has 7 protons and 7 neutrons in its nucleus, giving it a mass number of 14. Isotopes of elements are distinguished by their mass number; for example, carbon-12 and carbon-14 have mass numbers of 12 and 14 respectively.
2. Also called nucleon number
3. Compare atomic mass

Word History and Origins

Origin of mass number¹

First recorded in 1920–25

Example Sentences

As an example, the masses and radii of all nuclei up to mass number 50 were calculated using this method.

From Science Daily

“I remember being fixated on the fat mass number and thinking I better be leaner to be a better runner,” Bullat said.

From Seattle Times

According to passengers, the Boeing 777 made a sudden drop quickly and unexpectedly, causing a mass number of injuries to take place.

From Fox News

“It’s going to be the deployment of a mass number of people aimed at using direct action to shutting down the parade.”

From Washington Post

Given the mass number of people that saw their credit scores fall, and the special circumstances that surrounded it, is it time to reconsider our credit scoring system?

From Forbes