Atomic theory
Structure of the atom
Everything in the world is made up of The smallest part of an element that can exist.. The structure of the atom is what gives an element its chemical and physical properties.
Atoms are made up of three smaller particles:
Electrons
Negatively charged particles that spin around the positive centre of the atom in circles called energy levels. Their mass is so small it is nearly zero.
Protons
Positively charged particles that are contained in the The central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. The plural of nucleus is nuclei. of the atom (the centre) they have a mass of 1 amu (atomic mass unit).
Neutrons
Particles with no charge that are also contained in the nucleus of the atom. They also have a mass of 1 amu.
The nucleus has an overall positive charge as it contains the protons.
| Particle | Mass | Charge | Location |
| Electron | Approx 0 | -1 | Energy level |
| Proton | 1 amu | +1 | Nucleus |
| Neutron | 1 amu | 0 | Nucleus |
| Particle | Electron |
|---|---|
| Mass | Approx 0 |
| Charge | -1 |
| Location | Energy level |
| Particle | Proton |
|---|---|
| Mass | 1 amu |
| Charge | +1 |
| Location | Nucleus |
| Particle | Neutron |
|---|---|
| Mass | 1 amu |
| Charge | 0 |
| Location | Nucleus |
Every atom has no overall charge (neutral). While atoms do contain charged particles, they have the same number of positive protons as negative electrons. These opposite charges cancel each other out making the atom neutral.