Question

define periodicity?

Answer 1

Periodicity, generally related to the so called "invention" of the Periodic Table. In that table, Mendeleev arrange elements according to their molecular mass into rows and columns. Elements in the same columns have similar properties. Periodicity, in terms of Chemistry is the properties of elements that, if you know where it is in the Periodic Table, you can actually "predict" its properties without actually trying to find them out yourself. Periodicity is caused by regular and predictable variations in element atomic structure.

Periodicity is also the quality or state of being periodic; recurrence at regular intervals.