Question

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 charge experienced by valence electrons explain each specially vth point.

Answer 1

The vertical column in modern periodic table is known as group 1) no of valence electrons is the same in a group. 2)no of occupied shells increases down a group. 3)size of atoms increases because no of shells increases 4)metallic character of atoms increases because the electrons are fairly far away from the nucleus as the size increases.So it is easier for the heavier elementsto lose electrons .Hence they are more metallic. 5) Effective nuclear charge decreases down the group. This is due to shielding effect by the inner electrons.It essentially means that due to the presence of these electrons,outer electrons are less exposed to nuclear attraction.So,the net nuclear force of attraction on them decreases,as they're far away from the nucleus.

Answer 2

groups are vertical columns in a modern periodic table
1. valence electrons remains same because as we move down a group ,atomic no. change by 8 and shells are also increasing. so valence electrons remain constant
2. no. of shells increase down a group
3. size of atoms increase due to the increase in no. of shells
4. metallic character increase due the increase in atomic size for that reason it's ability to lose electrons increases so metallic character increases
5. nucleus charge decrease because of the increases in no. of shells the force between nucleus and outermost shell decrease so nucleus charge decrease