An atom X has a mass number of 35 and contains 17 electrons. Find the number of protons, electrons, and neutrons, along with the atomic number of the ion X${}^{–}$.

The correct option is B 17, 18, 18, 17

Electrons are gained during the formation of an anion.

For $X^{-}$,
Number of electrons = 17 + 1 = 18

For a neutral atom,
Number of protons = Number of electrons

The number of protons and neutrons does not change during ion formation.
Number of protons = Number of electrons in the neutral atom = 17

Atomic number = Number of Protons = 17
Mass number = Number of protons + Number of neutrons
35 = 17 + Number of neutrons
⇒ Number of neutrons = 35 – 17 = 18