Structure of the atom
The nuclear model
Atoms contain three sub-atomic particles called Subatomic particle with a positive charge and a relative mass of 1. The relative charge of a proton is +1., Uncharged subatomic particle, with a mass of 1 relative to a proton. The relative charge of a neutron is 0. and Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons..
The protons and neutrons are found 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. at the centre of the atom. The nucleus is very much smaller than the atom as a whole. The electrons are arranged in shells around the nucleus.
Properties of sub-atomic particles
| Particle | Relative mass | Relative charge |
| Proton | 1 | +1 |
| Neutron | 1 | 0 |
| Electron | \(\frac{1}{1836}\) This can be described as negligible (almost zero). | –1 |
| Particle | Proton |
|---|---|
| Relative mass | 1 |
| Relative charge | +1 |
| Particle | Neutron |
|---|---|
| Relative mass | 1 |
| Relative charge | 0 |
| Particle | Electron |
|---|---|
| Relative mass | \(\frac{1}{1836}\) This can be described as negligible (almost zero). |
| Relative charge | –1 |
The number of electrons in an atom is always the same as the number of protons, so atoms are electrically An object that does not have a positive or negative charge. overall.
Atoms can lose or gain electrons. When they do, they form charged particles called ions:
- if an atom loses one or more electrons, it becomes a positively charged ion
- if an atom gains one or more electrons, it becomes a negatively charged ion