Question

What isotope has \[18\] protons and \[22\] neutrons \[?\]

Answer 1

Hint: Here we have to find the element which has \[18\] protons. We have to check, the atom which has \[18\] protons and \[22\] neutrons is an isotope or not.

Complete step by step answer:
Isotope is one of two or more variants of atoms of a chemical element with the same atomic number and position in the periodic table and nearly identical chemical behaviour but with different atomic masses and physical properties. Every chemical element has one or more isotopes.
Simply, all isotopes of a given element have the same number of protons but different numbers of neutrons in each atom. For example, uranium-\[235\] and uranium-\[239\] are two different isotopes of the element uranium.
 Given the number of protons is \[18\]. So, the atomic number is also \[18\], and the element with atomic number \[18\] is Argon with the symbol \[Ar\].
 Now we need to find the mass number of Argon.
Because, Mass number \[ - \]Atomic number\[ = \]No of neutrons
Number of Neutrons\[ = 22\]. Hence, mass number of Argon is \[40\]
 Since, a neutral atom of argon also has 22 Neutrons.
So, it is clear that this is not an isotope but a neutral atom of Argon.

Note:
Note that when an atom has an equal number of electrons and protons, mains it has an equal number of negative electric charges (the electrons) and positive electric charges (the protons). Hence, the total electric charge of the atom is zero then the atom is said to be neutral.