TOPIC: PHYSICS OF RADIATIONπ IMPORTANT POINTS TO REMEMBERΒ πΉJohn Dalton in 1808 developed his famous βTheory of Atomβ.πΉElemental matter: It is made up of a combination of a single type of atom, e.g. hydrogen atom.πΉCompound matter: It is composed of recurring units of a specific number of atoms in a definite arrangement and at least two are different atoms. For example, sodium and chlorine combine to form a compound called sodium chloride, better known as common salt.
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