Structure of the atom
Nucleus and shells
An The smallest part of an element that can exist. has a central 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. surrounded by Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. arranged in areas called shells.
The nucleus is very small compared to the atom as a whole:
- as electrons are even smaller, most of an atom is empty space
- the diameter of a nucleus can be 100,000 times less than the diameter of an atom
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Subatomic particles
The Nuclei is the plural of nucleus. The nucleus is the central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. of all atoms contain Objects found in atoms, including protons, neutrons and electrons. called Subatomic particle with a positive charge and a relative mass of 1. The relative charge of a proton is +1. and most also contain Uncharged subatomic particle, with a mass of 1 relative to a proton. The relative charge of a neutron is 0..
The The amount of matter an object contains. Mass is measured in kilograms (kg) or grams (g). of subatomic particles are very tiny. Instead of writing their actual masses in kilograms, we often use their The relative mass is the number of times heavier a particle is, compared to another.. The relative mass of a proton is 1, and a particle with a relative mass smaller than 1 has less mass.
The mass of electrons is very small compared to protons and neutrons. Since a nucleus contains protons and neutrons, most of the mass of an atom is concentrated in its nucleus.
Protons and electrons have opposite electrical An imbalance of electrons and protons in a material. An excess of electrons results in negative charge, a deficit of electrons results in positive charge..
| Subatomic particle | Relative mass | Relative charge |
| Proton | 1 | +1 |
| Neutron | 1 | 0 |
| Electron | \(\frac{1}{1835}\) | -1 |
| Subatomic particle | Proton |
|---|---|
| Relative mass | 1 |
| Relative charge | +1 |
| Subatomic particle | Neutron |
|---|---|
| Relative mass | 1 |
| Relative charge | 0 |
| Subatomic particle | Electron |
|---|---|
| Relative mass | \(\frac{1}{1835}\) |
| Relative charge | -1 |
More guides on this topic
- Formulae and equations - Edexcel
- Hazards and risks - Edexcel
- The periodic table - Edexcel
- Ionic compounds - Edexcel
- Simple molecular substances - Edexcel
- Giant covalent substances - Edexcel
- Metals and non-metals - Edexcel
- Calculations for all students - Edexcel
- Higher tier only calculations - Edexcel
- Sample exam questions - key concepts in chemistry - Edexcel