Atomic Number

Atomic Number:

 The atomic number is equal to the number of positively charged protons in an atom’s nucleus and determines which element an atom is. The atomic number is unique for each element and is designated by a subscript to the left of the elemental symbol.
The atomic number for hydrogen is 1; it has one proton.
Elements are substances made up of atoms with
the same atomic number. Most of the elements are metals
(75 percent), and the others are nonmetals.