The different atomic forms of an element are called isotopes.

Here's what you need to know about isotopes:

* Same element, different number of neutrons: Isotopes of the same element have the same number of protons (which defines the element), but they differ in the number of neutrons.

* Similar chemical properties, different physical properties: Isotopes of an element have similar chemical properties because they have the same number of electrons, which determine how an atom interacts with other atoms. However, isotopes can have slightly different physical properties due to their differing masses.

* Examples: For example, carbon has two common isotopes: carbon-12 (6 protons and 6 neutrons) and carbon-14 (6 protons and 8 neutrons). Both are carbon, but carbon-14 is radioactive.

Let me know if you'd like more details on a specific isotope or have further questions!