Inorganic Chemistry 8.3


More trends in the properties of period 3 elements 

Some key properties of atoms such as size and ionisation energy are periodic.

Atomic radii

Becuase you cannot measure the radius of an isolated atom, half the distance betwqeen the centres of a pair of atoms is used. The atomis radius can differ, as it is a general term. The type of bond it has formed can effect the radius. Usually, the covalent radius is used to measure the size of an atom. Atomic radius is a pperiodic property asit decreases across the period and there is a jump when starting the next period, and atoms get larger down any group. 

Why the radius of an atom decreases across a period

Asyou go across a period you are adding protons, for example from sodium to chlorine the charge goes from +11 to +17. The increased charge pulls the electrons in closer to the nucleus, as there are no additional electron shells to prodive more sheilding, the


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