Exceptions of metallic elements :
(1) All metals except mercury are solids at room temperature, while mercury is a liquid at room temperature.
(2) Generally, metals have high melting points but Galium and Caesium have very low melting points.
(3) Alkali metals (Lithium, sodium, potassium) are very soft hence, they can be cut with a knife, while other metals cannot be cut with a knife.
Exceptions of non - metallic elements :
(1) Generally, non - metals exist as solids or gases at room temperature while bromine is a liquid.
(2) Non-metals does not possess lustre, but iodine is the only non-metal which possesses lustre.
(3) Non-metals have low melting points, but the diamond, an allotrope of carbon possesses very high melting point.
(4) Non - metals are generally non - conductors of electricity, but the graphite, an allotrope of carbon is the only non-metal which conducts electric current.