Here's why:
* Isotopes: Atoms of the same element can have different numbers of neutrons. These variations are called isotopes.
* Atomic Number vs. Mass Number:
* Atomic number defines the element and is equal to the number of protons in the nucleus.
* Mass number is the total number of protons and neutrons in the nucleus.
* Example: Carbon (C) has an atomic number of 6, meaning all carbon atoms have 6 protons. However, there are common isotopes of carbon:
* Carbon-12: 6 protons + 6 neutrons
* Carbon-14: 6 protons + 8 neutrons
The number of neutrons can affect the atom's mass and stability. Some isotopes are radioactive, meaning they decay over time.
