What is meant by ‘group’ in the modern periodic table? How do the following change on moving from top to bottom in a group? (i) Number of valence electrons (ii) Number of occupied shells (iii) Size of atoms (iv) Metallic character of elements (v) Effective nuclear change experienced by valence electrons.
The vertical columns in a periodic table are called groups. (i) All the elements of a group have the same number of valence electrons. (ii) On moving down in a group the number of occupied (filled) shells increases gradually. (iii) On going down in a group the size of atoms increases because a new shell of electrons is added to the atoms at every step. (iv) On going down in a group the metallic character of elements increases. (v) On moving down in a group, one more electron shell is added at every stage and size of the atom increases. Thus valence electrons move more and more away from the nucleus and hold of the nucleus or nuclear charge on valence electrons decreases.
