1. Section 2- Compounds, Chemical Formulas, and Covalent bonds
Chapter 8
Section 2- Compounds, Chemical Formulas, and Covalent bonds

2. Compounds Compounds- a substance made up of two or more elements
The compound has different properties from the elements that make up the compound
Ex- NaCl- common table salt
Na- Is a bright, soft metal when it is purifies
Cl- is a gas at room temperature
However, when combined they make a compound that is used as a seasoning for foods.

3. Chemical bonds A chemical bond is a force that joins atoms together
Bonds can be formed in two ways
Sharing electrons (Covalent bonds)
Giving/Receiving electrons (Ionic Bonds)

4. Covalent Bond
A covalent bond is a chemical bond formed when two atoms share one or more pairs of valence electrons
Generally non metals form these kinds of bonds
Each element in the bond wants to reach noble gas status
Each element wants to share electrons so that each has 8

5. Numbers of Covalent Bonds
A single covalent bond occurs when two atoms share one pair of valence electrons
A double covalent bond occurs when two atoms share two pairs of valence electrons
A triple covalent bond occurs when two atoms share three pairs of covalent bonds
Strength of bonds
Strongest- Triple
Weakest-Single

6. Covalent compounds
The bonds in water, carbon dioxide, and sugar are very different but they do have some similarities
Low melting and boiling points
Usually gases or liquids at room temperature
Poor conductors of thermal energy and electricity

7. Molecules
The chemically stable unit of a covalent compound is a molecule
A molecule- is a group of atoms held together by covalent bonding that acts as a single or independent unit
For example- Table sugar is C₁₂H₂₂O₁₁
One grain of sugar is made up of millions of sugar molecules
One molecule would be made up of 12 Carbon atoms, 22 Hydrogen atoms, and 11 Oxygen atoms

8. Water and Other polar Molecules
In a covalent bond, one atom can attract the other atom more strongly
For example, in water the Oxygen attracts the Hydrogen more
The Oxygen is more negative and has a partial negative charge
The Hydrogen has a partial positive charge
A molecule that has a partial negative and a partial positive charge because of unequal sharing of electrons is POLAR COVALENT

9. Nonpolar molecules
Usually occurs when the same atom is bonded with itself
Also occurs when the electrons are shared equally
Non polar compounds dissolve easily in other non polar compounds but not so well in polar compounds
“Like dissolves like”

10. Chemical Formulas and molecular Models
A chemical formula is a group of chemical symbols and numbers that represent elements and the number of atoms of each element.
“like a recipe”
CO₂ means one atom of carbon and 2 atoms of oxygen
The subscripts shows the quantity of the element
The formula DOES NOT SHOW THE SHAPE OF THE MOLECULE