The mass number of argon is 40. Which one of the following statements

The mass number of argon is 40. Which one of the following statements is correct?

The number of protons in argon is 22.
The number of neutrons in argon is 18.
The number of electrons in argon is 18.
The sum of numbers of protons and electrons in argon is 40.
This question was previously asked in
UPSC NDA-1 – 2022
The number of electrons in a neutral atom of argon is 18.
The mass number of an element is the sum of the number of protons and neutrons in the nucleus. The atomic number, which defines the element, is equal to the number of protons. In a neutral atom, the number of protons is equal to the number of electrons. Argon (Ar) has an atomic number of 18.
Given mass number = 40. Atomic number of Argon = 18. Number of protons = 18. For a neutral atom, number of electrons = number of protons = 18. Number of neutrons = Mass number – Number of protons = 40 – 18 = 22.