from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The sum of the number of neutrons and protons in an atomic nucleus. Also called nucleon number.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The total number of protons and neutrons in an atomic nucleus.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. the sum of the number of neutrons and protons in an atomic nucleus
Sorry, no etymologies found.
Nitrogen is the commonest gas in the atmosphere and its mass number is 14, the same as carbon-14’s.