Covalent Bond: When two non-metals share electrons from their valence shell.
Weaker than ionic bonds.
Their melting/boiling points are low and their electrical conductivity is terrible.

Lone Pairs: Pairs of electrons that don’t interact in the bond.

Octet Rule:
Atoms are always trying to have 8 electrons in their valence shell, which is why atoms form bonds to share electrons so they have 8 together.

Duplet Rule:
Small atoms like hydrogen and helium only have ONE shell that can hold 2 electrons max, so some small atoms follow this rule, which is why Helium is “perfect”.
H, He, Li, Be, and B are duplets.

Electronegativity:
A scale from 0 to 4 says how desperate an element is to get electrons, and it increases when going UP and RIGHT on the periodic table, so Flourine is the highest value of 3.98.

Polarity:
The difference in electronegativity can cause a dipole, which means that one part of the molecule is partially negative and another is partially positive, then the bond/molecule is polar.
Whereas, if the difference is under 0.5 then it is considered non-polar.
Also if the molecules are symmetrical then it is non-polar.

Polar and non-polar molecules DON’T mix, which is why when you pour oil on water, then don’t mix.

Ionic Bonds:
When an atom gives away 1 or more electrons to another atom, which makes them more stable.
They are usually dissolved in water and they are SUPER sensitive to pH changes.

Ionic compounds:
ALMOST ALWAYS = Metal + Non-Metal.
The result of an ionic bond, so NaCl and other “salts”.
Most are arranged in 3D arrays called crystals.
We talk about it “globally”, AKA that the bond is between many ions, not just two.

Energy Needed to form bond:

Net Change in Energy:
The energy required to form an anion MINUS the energy released from the cation.

Lattice Energy:
The net change MINUS the energy of the compound
Results in a MASSIVE decrease, which makes the bond hard
As the LOWER energy the more stable.
So the HIGHER the charge the HIGHER lattice energy
AND
The SMALLER radii give HIGHER lattice energy

Strength of Interaction between ions:
The greater the charges, the STRONGER, so 2+ > 1+
The SMALLER radii, the STRONGER, so they can be CLOSER together