* Atoms of the same element can have different numbers of neutrons but must always have the same number of protons.

* This is because the number of protons determines the element, while the number of neutrons determines the isotope of the element.

Here is a more detailed explanation:

* The atomic number of an element is the number of protons in the nucleus of an atom of that element.

* The mass number of an element is the total number of protons and neutrons in the nucleus of an atom of that element.

* Isotopes are atoms of the same element that have different mass numbers.

* This is because isotopes have the same number of protons but different numbers of neutrons.

For example, carbon has three naturally occurring isotopes: carbon-12, carbon-13, and carbon-14.

- Carbon-12 has 6 protons and 6 neutrons.

- Carbon-13 has 6 protons and 7 neutrons.

- Carbon-14 has 6 protons and 8 neutrons.

All three isotopes of carbon have the same number of protons (6), but they have different numbers of neutrons (6, 7, and 8, respectively).