Types of Compounds
Periodic Table
The periodic table is divided into two major divisions: metals and non-metals. Metals (shown below in yellow) are located on the lower left and include typical metals such as iron (Fe) and nickel (Ni). Non-metals (shown in blue) are located in the upper right and include oxygen and nitrogen (common gases) as well as iodine (a solid). Note that hydrogen (H) is considered a non-metal even though it is in the first column. The position of elements on the periodic table can to used to predict with a high degree of accuracy the structure of a wide range of compounds.
Classes of Binary Compounds
A binary compound is one that is formed from two types of elements. Three possibilities exist.
| metal + metal | ¾® | metallic compound |
| metal + non-metal | ¾® | ionic compound |
| non-metal + non-metal | ¾® | covalent compound |
The physical properties of each of these types of compounds is summarized below.
| Metals | Ionic | Covalent | |
| Melting points | variable | high | low |
| Electrical conductivity |
high | low (solutions do conduct) |
low |
| Hardness | hard | hard | soft |
| Brittle | malleable | brittle | brittle |