(a) Isotopes of an element have same atomic number as well as electronic configuration , distribution. Since the chemical properties of elements are related to their electronic configuration i.e., the elements with similar configuration will have similar properties. Thus, the isotopes of an element are chemically similar.
(b) In an atom, the number of protons in the nucleus is equal to the number of electrons in the extra nuclear portion. Since each proton and each electron has the same charge but with opposite magnitude, the atom is electrically neutral.
(c) The atoms of noble gas elements have complete outermost shells. Hence, they are least reactive.
(d) Nucleus of an atom is made-up of protons which are positively charged and neutrons that are neutral. The total mass of neutron and proton make it heavy.
(e) When an atom changes into an ion (cation or anion) the valence shell of the ion has a complete octet or duplet.