1. Atoms, Molecules, Elements, and Compounds

2. Atoms
Atom: The basic unit of a chemical element

3. Elements
Elements are called the building blocks of matter because all matter is composed of elements.
Each element is made up of the same type of atoms.
Hydrogen (H)
Oxygen (O)
Carbon (C)

4. Molecules
A molecule is formed when two or more atoms join together chemically.
Hydrogen – H2
Oxygen – O2

5. Compounds
A compound is a substance made of two or more different kinds of elements
Each compound is represented by a formula that uses symbols to identify which elements are present.
A formula shows the ratio of elements in the compound.
H2O – 2 Hydrogens and 1 Oxygen

6. Compounds

7. What is the difference between a compound and a molecule?
A molecule is formed when two or more atoms join together chemically.
A compound is a molecule that contains at least two different elements.
All compounds are molecules but not all molecules are compounds.

8. NaCl is the formula for salt

9. Water is H2O
An oxygen atom can bond with two hydrogen atoms to make a molecule we call water. Water is an example of a compound, because it contains more than one kind of atom. The formula for water is H2O, meaning there are two hydrogen atoms for each oxygen atom.

10. Carbon Dioxide CO2
Carbon dioxide molecules are made from one carbon and two oxygen atoms joined together by covalent bonds. The chemical symbol is CO2. This is another compound!

11. DNA
Is a large molecule made up of carbon, hydrogen, nitrogen, oxygen, and phosphorous.