1. **Key Concepts:**
1.1. **Atoms:** The smallest particles that make up all matter. They consist of a nucleus (center) with protons and neutrons, and electrons orbiting around the nucleus.
1.2. **Elements:** Substances made up of one type of atom. Each element is unique and identified by its atomic number.
1.2.1. Elements can be classified into two groups based on their properties: **metals and non metals**
1.2.2. **Compounds:** Two or more elements combined chemically in fixed proportions which can be represented by formulae (When atoms of different elements combine to form new substances with unique properties.) **compounds have different properties as the elements that make them up**
2. **The three states of matter**
2.1. These describe how particles are arranged into solids liquids and gases, and how this changes during freezing, melting condensing and boiling.
2.1.1. **Solid:** hard to compress because the particles are packed together in a regular pattern. They have a fixed shape and cannot flow from place to place. The particles can vibrate but they cannot move from one place to another.
2.1.2. **Liquids:** Are also hard to compress, because like solids the particles are close together with limited space between them. **However** liquids can change shape and flow from one place to another.
2.1.3. **Gases:** Unlike Solids and Liquids are very easy to compress because the particles move quickly and randomly.
2.2. **We can change the states of a substance by putting in or taking out energy**
3. **Ionic Bonding**
3.1. Elements react so they achieve a **full outer energy level**, qhich is also called the **electronic structure of a noble gas**
3.2. When a metal reacts with a non-metal, this is called ionic bonding.
3.2.1. **Group 1 metals** lose 1 electron forming a 1+ ion
3.2.2. **Group 7 non-metals** gain 1 electron forming a 1- ion.
3.2.3. **Group 2 metals** lose 2 electrons forming a 2+ ion.
3.2.4. **Group 6 non-metals** gain 2 electrons formins a 2- ion.