Question

What is perodicity in properties ?

Answer 1

Periodicity in properties means the repetition of properties of elements in the periodic table.
As the elements are ordered in the periodic table by increasing atomic mass, certain properties of elements like atomic radius, number of valence electron, electronegativity etc show a particular trend.

Answer 2

Periodicity refers to similarities is the properties of the element in the periodic table.
When Mendeleev Arranged the elements in the periodic table it is found that many of the properties like Atomic radii,Electron gain enthalphy,electron negativity and Ionisation energy are found to be similar for some elements.