The number of in an atom of an element is the element's atomic number

The number of protons in an atom is the atom's atomic number.
In a neutral atom the number of protons is equal to the number of electrons.
There is possibility of losing the electrons, but the number of protons are not loosed, except in nuclear chemistry.
So the number of protons is equal to the atom's atomic number.

Atomicity occurs to prevent updates of the database occurring only partially, which can cause greater problems than rejecting the whole series outright.some are monatomic, diatomic, triatomic etc because it shows the number of atoms. for example, monatomic means it contains only one atom.