Question

An atom with atomic number 9 and mass number 19 will have the following constituents:

A. 9p, 9n, 9e

B. 9p, 10n, 9e

C. 10p, 9n, 9e

D. 9p, 9n, 10e

Answer 1

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