What's the Same:
* Atomic Number (Number of Protons): Isotopes of the same element *always* have the same number of protons. This is what defines the element. For example, all carbon atoms have 6 protons.
* Chemical Properties: Isotopes of the same element generally have very similar chemical properties. This is because their electron configurations (arrangement of electrons) are the same.
What's Different:
* Mass Number (Number of Protons + Number of Neutrons): Isotopes differ in the number of neutrons they have. This is why they have different atomic masses. For example, carbon-12 has 6 neutrons, while carbon-14 has 8 neutrons.
* Physical Properties: Isotopes can have slightly different physical properties, like melting point or density, due to their different mass.
In Summary:
Two atoms are isotopes of the same element if they have the same number of protons (atomic number) but a different number of neutrons (mass number).
