Final answer:
Atoms of the same element with different numbers of neutrons are known as isotopes. They share the same atomic number but have different mass numbers, affecting their atomic mass but not their chemical behavior.
Step-by-step explanation:
Atoms of the same element that have different numbers of neutrons but the same number of protons and electrons are called isotopes. Each isotope of a given element has the same atomic number (Z) but a different mass number (A), which is the sum of the numbers of protons and neutrons. For instance, hydrogen has isotopes such as protium with 0 neutrons, deuterium with 1 neutron, and tritium with 2 neutrons, but they all share the atomic number 1, signifying the single proton that defines hydrogen as an element.
Isotopes exhibit the same chemical properties because they have the same number of protons and electrons. However, they can greatly differ in atomic mass and, in some cases, nuclear stability. Different isotopes of an element can occur naturally and are particularly useful in various scientific and medical applications due to their different physical properties.