How does covalent radii vary in a period as well as in a group in the periodic table ? What is the reason ?

How does covalent radii vary in a period as well as in a group in the

1.	How does covalent radii vary in a period as well as in a group in the periodic table ? What is the reason ?
Answer» SOLUTION :In a period as we have from left to left to right covalent radius decreases in a period. As we move from left to right atomic number or nuclear charge increases. The pull of the ELECTRON cloud by the nucleus increases, the electron cloud shrinks and as a result the covalent radius decreases. In a GROUP . covalent radius increases from top to bottom . In a group as we move from top to bottom one by one new orbitals are ADDED up thereby the size of the atom goes on INCREASING . The atomic radius also goes on increasing.