Explain the following :

(a) Mass of an atom is concentrated inside the nucleus of the atom.

(b) Atoms combine by transfer and sharing of electron(s).

(c) An element has atoms with different mass number.

(d) Carbon-12 and carbon-14 both show similar chemical properties

(a) Atom is made of primarily three sub-atomic particles namely electrons, protons and neutrons. An electron has negligible mass, and protons and neutron lie inside the nucleus, hence, mass of an atom is majorly present in the nucleus.

(b) Elements tend to combine with one another to attain the stable electronic configuration of the nearest noble gas. This is achieved either by gaining electrons or losing electrons or sharing of electrons with other atoms of the same element or another element to form a chemical compound.

(c) Isotopes are the elements having the same atomic number but different mass numbers.

For example : ²⁴₁₂Mg and ²⁶₁₂Mg

Isotopes differ in the number of neutrons.

(d) Chemical properties are determined by the electronic configuration of an atom and electronic configuration of both isotopes of carbon is same, i.e., electronic configuration of C-12 is [2,4] and electronic configuration of C-14 is [2,4], hence they both have same chemical properties.