Question

The presence of positive charge on the nucleus is due to the protons in the nucleus. As established earlier, the charge on the proton is equal but opposite to that of electron. Atomic number (Z) = number of protons in the nucleus of an atom = number of electrons in a neutral atom. protons and neutrons present in the nucleus are collectively known as nucleons. The total number of nucleons is termed as mass number (A) of the atom. mass number (A) = number of protons (Z) + number of neutrons (n). Isobars are the atoms with same mass number but different atomic number for example, 6¹⁴C and 7¹⁴N. On the other hand, atoms with identical atomic number but different atomic mass number are known as Isotopes. For example, considering of hydrogen atom again, 99.985% of hydrogen atoms contain only one proton. This isotope is called protium (1¹H). Rest of the percentage of hydrogen atom contains two other isotopes, the one containing 1 proton and 1 neutron is called deuterium (2 1D, 0.015%) and the other one possessing 1 proton and 2 neutrons is called tritium (1 3 T).