Explain : We cannot classify the elements according to their physical

1.	Explain : We cannot classify the elements according to their physical properties alone.
Answer» Solution : 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.

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