Compounds

1. Compounds • A compound contains two or more atoms joined with a characteristic ratio. • Law of constant composition – molecules of the same compound will combine in a prescribed ratios of the elements that combine to make it up. • Example sodium chloride combines in a 1:1 ratio.

2. Types of compounds • Organic compounds contain carbon and usually hydrogen. • Inorganic compounds do not contain carbon.

3. Molecule – a distinct group of atoms bonded together. • Ion – a positively or negatively charged atom or group of atoms. • Molecular compounds – compounds comprised of molecules • Ionic compounds – consist of ions.

4. Molecular Compounds • Structural formula – a representation of a compound. • There are several common types such as ball-and-stick model, tube structure, and space-filling model.

5. Ball-and-stick model

6. Tube structure

7. Space-filled model

8. Molecular models indicate the size and shape of molecules. • The molecular formula of a molecular compound indicates the number of atoms of each type of element present in the molecule.

9. Ions and Ionic Compounds • Positively charged ions are called cations. • Negatively charged ions are called anions. • Monatomic ions are charged particles containing only one atom. • Elements in groups 1-14 tend to form positive ions when they are monatomic.

10. Elements in groups 15-17 tend to form negative monatomic ions. • Group 1 elements will always have monatomic ions with a charge of +1. (except hydrogen, +1 or -1) • Group 2 elements will always have monatomic ions with a charge of +2 • Group 13 elements tend to have a charge on +3 on their monatomic ions and group 14 +4

11. Group 3 elements have a charge of +3 • Group 17 elements have a charge of -1 • Group 18 elements have no charge because they do not form ions. • Zn and Cd always have a charge of +2 • Silver always has a charge of +1. • Oxygen almost always has a charge of -2. The exceptions are peroxides and super oxides.