2.3 explain the classification of elements as metals or non-metals on the basis of their electrical conductivity and the acid-base character of their oxides

Elements are classified as metals if they conduct electricity (because they allow a charge to pass through them easily). Metal oxides are basic, meaning they will neutralise acids, if metal oxides dissolve they will form a solution with pH of more that 7.

Elements are classified as non-metals if they are poor conductors of electricity. Non-metals are acidic and, if they dissolve, they will form a solution with a pH of less than 7.