* Atomic Number: The number of protons in an atom's nucleus determines its atomic number. A neutral atom has the same number of electrons as protons.
* Electron Shells: Electrons are organized into shells around the nucleus. Each shell can hold a certain maximum number of electrons.
* The first shell can hold up to 2 electrons.
* The second shell can hold up to 8 electrons.
* The third shell can hold up to 18 electrons.
* And so on.
* Valence Electrons: The electrons in the outermost shell are called valence electrons. These are the ones most involved in chemical bonding.
Example:
* Hydrogen (H): Atomic number 1. It has 1 proton and 1 electron.
* Carbon (C): Atomic number 6. It has 6 protons and 6 electrons (2 in the first shell, 4 in the second).
* Oxygen (O): Atomic number 8. It has 8 protons and 8 electrons (2 in the first shell, 6 in the second).
Important Note: Atoms can gain or lose electrons to become ions, which have a positive or negative charge.
