What is the cause of the periodicity in the properties of the elements

1.	What is the cause of the periodicity in the properties of the elements? How do the following properties vary in (a) a group and (b) in a period (i) electronegativity (ii) ionisation enthalpy (iii) Atomic size
Answer» It is due to the similarity in the outer electronic configurations which gives rise to the periodic properties of the elements. (a) In a group: (i) Electronegativity- It decreases down the group. (ii) Ionisation enthalpy- It decreases down the group. (iii) Atomic size- It increases down the group. (b) In a period: (i) Electronegativity- Increases (ii) Ionisation enthalpy- Increases (iii) Atomic size- Dereases.

What is the cause of the periodicity in the properties of the elements? How do the following properties vary in (a) a group and (b) in a period (i) electronegativity (ii) ionisation enthalpy (iii) Atomic size

Answer»

It is due to the similarity in the outer electronic configurations which gives rise to the periodic properties of the elements.

(a) In a group:

(i) Electronegativity- It decreases down the group.

(ii) Ionisation enthalpy- It decreases down the group.

(iii) Atomic size- It increases down the group.

(b) In a period:

(i) Electronegativity- Increases

(ii) Ionisation enthalpy- Increases

(iii) Atomic size- Dereases.