Pure Substances are made of only one kind of substance and has constant properties and composition. These cannot be physically separated.
Elements are the fundamental substances that are made of only one kind of atom. These cannot be any more physically or chemically simplified or decomposed.
- Metals — Small number of Valence Electrons; donates Electrons during Ionic Bonding; forms Cations when ionized. E.g. Potassium
- Non-metals — Valence Electrons are close to completing the Octet Rule. accepts Electrons during Ionic Bonding; forms Anions when ionized; properties are opposite of those of metals; liquid or gas or brittle solids at room temperature. E.g. Oxygen
- Metalloids — Has the physical properties of both metals and non-metals; can act as a metal or a non-metal depending on the conditions. E.g. Silicon (semiconductor)
Compounds are made up of only one type of Molecule that are composed of two or more Elements and can be separated into simpler substances and elements by chemical methods only.
- Ionic — Components are a pair of Anions group and a Cations group. Electrons are transferred from the Cations to the Anions, usually formed when Metals react to Non-metals. E.g. NaCl
- Covalent — Components are both Anions. Electrons are shared within the bond, formed when two Non-metals react with each other. E.g. CO2
- Metallic — Components are both Metals. Electrons are stored in a “sea of electrons.” E.g. AgNO2