# What are electrons, protons and neutrons?

Protons and neutrons are massive particles that are conceived to constitute atomic nuclei. Protons have a unit positive charge, and neutrons are neutral. A strong nuclear force operates at $\text{nucular}$ distances that binds the nuclear particles together, and overcomes electrostatic repulsion.
The number of protons in a nucleus is the atomic number, $Z$, and identfies the element: $Z = 1 , \text{hydrogen}$; $Z = 2 , \text{helium}$; $Z = 3 , \text{lithium}$;.................$Z = 23 , \text{vanadium}$;.........................