The element argon has three naturally occurring isotopes, with 18, 20, and 22 neutrons in the nucleus, respectively. (a) Write the full chemical symbols for these three isotopes.

Key Concepts

Isotopes

Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons in their nuclei. This difference in neutron count results in varying atomic masses for the isotopes. For example, argon has isotopes with 18, 20, and 22 neutrons, leading to different atomic masses while retaining the same chemical properties.

Chemical Symbol

A chemical symbol is a one- or two-letter notation used to represent an element on the periodic table. The first letter is always capitalized, while any subsequent letters are lowercase. For isotopes, the chemical symbol is often accompanied by a superscript indicating the total number of protons and neutrons (mass number) and a subscript indicating the number of protons (atomic number).

Mass Number

The mass number of an isotope is the total count of protons and neutrons in its nucleus. It is represented as a superscript in the isotope's chemical symbol. For instance, the isotopes of argon can be denoted as ¹⁸Ar, ²⁰Ar, and ²²Ar, where the numbers 18, 20, and 22 represent the mass numbers corresponding to the different neutron counts.