eolas/Electronics/Physics_of_electricity/Matter_and_atoms.md

---
categories:
  - Electronics
tags: [physics]
---

# Matter and atoms 

## Matter, elements, compounds and mixtures

- Matter is anything that occupies space and has weight. It may be found in any one of three states:  liquid, solid, or gas.
- Matter can be classed in terms of **elements**, **compounds** and **mixtures**.
  - An element is a substance that cannot be reduced to a simpler substance by chemical means. 
  - The chemical combination of two or more elements is a compound. Compounds _can_ be separated by reduced by chemical means but they cannot be physically separated.
  - A _physical_ (note not _chemical_) combination of elements and compounds is a mixture. 
  - For example "air" is a mixture which is made up of oxygen, nitrogen, carbon dioxide, and other gases.
  
## Atoms and molecules

- Elements are made up of **atoms**. 
-  A **molecule** is a type of compound where the atoms of two types of elements have joined together. For example Sodium and Chlorine are two elements that can join to form Sodium Chloride. We call this **chemical bonding**. 

## Atomic particles

* There are three particles comprising atoms: protons, neutrons and electrons.

* Protons and neutrons comprise the nucleous of the atom. A proton is positively charged. A neutron has no charge.

* Electrons orbit around the nucleous in concentric rings. Electrons are negatively charged. Because of this protons and electrons attract each other.