An element with the same number of protons but a different number of neutrons is called a:

An element with the same number of protons but a different number of neutrons is referred to as an isotope. This is because isotopes are variants of a particular chemical element that share the same atomic number, meaning they have the same number of protons. However, they differ in their atomic mass due to the varying number of neutrons present in the nucleus. This characteristic allows isotopes to retain the same chemical properties while having different physical properties, such as stability and radioactivity.

In contrast, protons and electrons refer to specific subatomic particles that make up an atom, with protons being positively charged and found in the nucleus, while electrons are negatively charged and located in the electron cloud surrounding the nucleus. Neutrons are also particles found in the nucleus but do not carry a charge. They play a crucial role in determining the stability of the nucleus, but by themselves, they do not define what an element is; rather, they contribute to the variants of that element known as isotopes.