From left to right across a period in the periodic table, elements become less and more in their properties

From left to right across a period in the periodic table, elements become less metallic and more nonmetallic in their properties.

The general trend across a period involves a decrease in metallic character and an increase in nonmetallic character. Elements on the left side of the periodic table (alkali metals and alkaline earth metals) are metals with metallic properties such as conductivity and luster. As you move to the right, elements become less metallic and more nonmetallic. Elements on the right side of the periodic table (halogens and noble gases) are nonmetals with properties such as poor conductivity and lack of metallic luster.

This trend is associated with changes in atomic structure, such as the increasing effective nuclear charge and the tendency of atoms to gain electrons to achieve a stable electron configuration.