Here's why:
* Energy Levels: Electrons in atoms exist in specific energy levels, like rungs on a ladder. The outermost energy level is called the valence shell.
* Stability: A full valence shell means the electrons are tightly bound and not easily pulled away. This gives the atom a low energy state, making it more stable.
* Reactivity: Atoms with incomplete valence shells tend to be reactive, meaning they want to interact with other atoms to achieve a full outer shell.
There are two main ways atoms achieve this:
* Gaining electrons: Non-metals (like oxygen) tend to gain electrons to fill their valence shell, forming negative ions.
* Losing electrons: Metals (like sodium) tend to lose electrons to empty their valence shell, forming positive ions.
This desire for a full outer shell drives chemical bonding, leading to the formation of molecules and compounds.
