If the atomic number of an element is how many protons and electrons it has, how do you find the
number of neutrons in an atom

number of neutrons in an atom = Mass number - atomic number

Explanation:

The atomic number of an element is equal to the number of protons and electrons it has.

The mass number is equal to the total number of protons and neutrons in an element.

The mass number is also called as atomic mass number or nucleon number.

So,

number of neutrons in an atom = Mass number - atomic number

b.

explanation:

vapour or gas assuming atmospheriv pressure