Question

explain the given peroidic properties variation in a groups in a period​

Answer 1

$\huge\tt\red{Answer:-}$

a). The horizontal rows of elements in a periodic table are called periods. Characteristics:  

(i) The elements in a period have consecutive atomic numbers.

(ii) The number of elements in period is fixed by the maximum number of electrons which can be accommodated in various shells.  

Characteristics:  

The vertical columns in a periodic table are called group characteristics  

(i) The elements in a group do not have consecutive atomic numbers.

(ii) All the elements in a group have similar electronic configuration and show similar properties.

(b). The size of atom decreases on moving from left to right in a period. As we move from left to right in a period the atomic number of elements increases  which means that the number of protons and electrons in the atom increases. The electronic configuration of the atoms increases in the same shell. Due to large positive charge on the nucleus the electrons are pulled in more close to the nucleus and the size of the atom decreases. On going down in a group of the periodic table the atomic size increases due to the increases in atomic shells.