Chemical Bonding

Atoms form bonds with each other to make molecules.

Atoms are stable when they have full valence (outermost) shells of electrons.
- The innermost shell can hold 2 electrons
- The next shell can hold 8 electrons
Electrons interactions cause atoms to bond and form molecules.
Bonds can be relatively weak (easy to break) or strong

Ionic Bonds

Ionic bonds form when oppositely charged atoms are attracted to each other.

Atoms can gain or lose electrons to have full valence shells
- If an atom like sodium has 1 electron in its outer shell, it will lose it so that the next inward shell becomes the outer shell.
- In an atom like fluorine, it only needs one electron to fill its outer shell; it will gain one.

Ions are atoms that have a charge.
- If an atom loses an electron, it becomes more positive (cation).
- If an atom gains an electron, it becomes more negative (anion).

Opposite charges are attracted to each other, so a cation and an anion stay close to each other, creating an ionic bond.

Ionic bonds are relatively weak, and can be broken by other atoms/molecules that have a charge.

Covalent Bonds form when atoms share electrons.

Atoms share as many electrons as it takes to fill their valence shell
- Sharing 2 electrons makes a double bond
- Sharing 3 electrons makes a triple bond
Covalent bonds are much stronger than ionic bonds
Polar Covalent bonds are formed when the molecule has relative positive and negative regions.
- Some atoms pull harder on electrons than others when they share
- When more electrons stay around one atom, it creates a negative region.
Polar molecules are neutral overall, but they can behave as though they have a charge
- Opposite charges can attract other ions or polar molecules
  - Hydrogen Bonds result from the attraction between oppositely charged polar molecules, they are weak.
- Like charges can repel other ions or polar molecules
- Polar molecules do not mix well with Non-Polar molecules.