Question

How do the following properties vary on moving from left to right across a periodic table?
(i) Atomic radius (ii) Electronegativity
(iii) Ionisation potential

Answer 1

(i) Atomic radius
On moving from left to right across a period, the atomic radius decreases.
With increase in atomic number, the nuclear charge increases but the number of shells in the atoms of all the elements in a period remains the same. The nuclear attraction of the outermost electron increases due to which the atomic radius decreases.
(ii) Electronegativity
On moving from left to right across a period, electronegativity increases.
With increase in atomic number, the nuclear charge increases but the number of shells in the atoms of all the elements in a period remains the same. The nuclear attraction of the outermost electron increases. Hence, tendency to attract shared pair of electrons increases from left to right in a period.
(iii) Ionisation potential
On moving from left to right across a period, ionisation potential increases.
With increase in atomic number, the nuclear charge increases but the number of shells in the atoms of all the elements in a period remains the same. The nuclear attraction of the outermost electron increases due to which ionisation potential increases.