Explain the salient features of periods in the modern periodic table.

Explanation

i) The vertical columns in the periodic table starting from top to bottom are called groups.
(ii) There are 18 groups in the periodic table.
(iii) As the elements present in a group have identical valence shell electronic configurations, they possess similar chemical properties.
(iv) Based on the common characteristics of elements in each group, they can be grouped as various families.
(v) The Lanthanides and Actinides which form part of Group 3 are called inner transition elements.
(vi) Except group 0, all the elements present in each groups have same valency.
(vii) The elements present in a group possess similar chemical properties.
(viii) The physical properties of the elements in a group such as melting point, boiling point and density vary gradually.
(ix) The atoms of the group 0 elements have stable electronic configuration in their valence shells and hence they are unreactive.