The number of protons present in an atom is known as atomic number of the atom. The positive charge of the nucleus is because of protons present in the nucleus. Number of protons in an atom determines the total positive charge on the nucleus or positive charge present in an atom. If an atom is neutral, then the number of electrons and number of protons present in the atom are equal. So, number of protons also determine the total negative charge present in the atom. Sum of number of protons and number neutrons in an atom are known as atomic mass. Therefore, number of protons in an atom also helps in determining the atomic weight.