Question

give reason why nucleus of an atom is positively charged​

Answer 1

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Rutherford deduced that the atomic nucleus was positively charged because the alpha particles that he fired at the metal foils were positively charged, and like charges repel. Alpha particles consist of two protons and two neutrons, so they are positively charged.

Answer 2

Because the nucleus is only made up of protons and neutrons it is positively charged.