All of the period 3 elements occur in nature and have at least one stable isotope.

The double bond rule states that chemical elements with a principal quantum number greater than 2 (e.g. Period 3 elements and lower) do not form multiple bonds (e.g. double bonds and triple bonds) with themselves or with other elements.

All of the period 3 elements occur in nature and have at least one stable isotope.

A period 3 element is an element found on the third period (row) of the periodic table.

The double bond rule states that chemical elements with a principal quantum number greater than 2 (e.g. Period 3 elements and lower) do not form multiple bonds (e.g. double bonds and triple bonds) with themselves or with other elements.