1.

An atom with atomic number 9 and mass number 19 will have the following constituents:A. 9p, 9n, 9eB. 9p, 10n, 9eC. 10p, 9n, 9eD. 9p, 9n, 10e

Answer»

We know that,

Atomic number = Number of protons = 9.

Hence, 9p

Mass number = Number of protons + Number of neutrons

⇒ 19 = 9 + Number of neutrons

⇒ Number of neutrons = 19-9 =10

Hence, 10n

Now, Number of electrons = Number of protons

⇒ Number of electrons =9

Hence, 9e

Therefore, the correct option is B



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