4. Structure Of Atoms
The number of protons present in the nucleus of an atom of an element is known as its atomic number.
Example. An atom of carbon has 6 protons so, the atomic number of carbon is 6. The atomic number is denoted by Z. Now positive charge on the nucleus is due to the presence of protons in it and each proton carries one unit of positive charge. Therefore, the atomic number of an element is equal to number of positive charges carried by the nucleus of an atom of the element.
Atomic number of an element (Z)
= Number of protons (p)
= Number of positive charges carried by the nucleus of the atom
or = Number of electrons (e)