What is the atomic number equal to?

1 Answer
Mar 29, 2016

#Z#, the atomic number is equal to the number of positively charged, massive nuclear particles.


#Z# is simply the number of nuclear protons, and this number defines the identity of the element. If #Z=1#, the element is hydrogen, If #Z=3#, the element is lithium, If #Z=35#, the element is bromine.

While the atomic number defines elemental identity, the atomic nucleus may contain various numbers of neutrons, massive, neutrally charged, nuclear particles. This gives rise to the existence of isotopes. Both protons and neutrons engage in the strong nuclear force, a short range force that is orders of magnitude greater than the repulsive electrostatic force between protons, and acts to bind the nucleus together.