Which of the following describes isotopes?

Isotopes are defined as atoms of the same element that have the same number of protons but different numbers of neutrons. This distinction is crucial because the number of protons in an atom determines its elemental identity, while variations in neutron count lead to differences in atomic mass and some physical properties.

For example, carbon has several isotopes, including carbon-12, which has six protons and six neutrons, and carbon-14, which has six protons and eight neutrons. While they share the same position on the periodic table as carbon due to having the same number of protons, their differing neutron counts result in variations in their atomic mass.

This answer captures the essence of what isotopes are, emphasizing the role of protons in defining an element and neutrons in creating variations among isotopes of that element. Understanding this concept is foundational for exploring topics like nuclear chemistry and atomic structure.