Atoms Molecules Elements and Compounds Atoms l Atom

Atoms, Molecules, Elements, and Compounds

Atoms l Atom: The basic unit of a chemical element

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

Molecules l A molecule is formed when two or more atoms join together chemically. l Hydrogen – H 2 l Oxygen – O 2

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

Compounds

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

Na. Cl is the formula for salt

Water is H 2 O l 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 H 2 O, meaning there are two hydrogen atoms for each oxygen atom.

Carbon Dioxide CO 2 l Carbon dioxide molecules are made from one carbon and two oxygen atoms joined together by covalent bonds. The chemical symbol is CO 2. This is another compound!

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