AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
The basic structure of an atom is a positively charged nucleus composed of…
Full specification wording
The structure of an atom: The basic structure of an atom is a positively charged nucleus composed of both protons and neutrons surrounded by negatively charged electrons.
An atom has a tiny central nucleus carrying positive charge because it contains protons, which are positively charged, and neutrons, which have no charge.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 2 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
An atom has a tiny central nucleus carrying positive charge because it contains protons, which are positively charged, and neutrons, which have no charge. The nucleus therefore has a positive overall charge equal to the number of protons. Surrounding the nucleus are negatively charged electrons, arranged in energy levels or shells. In a neutral atom the number of electrons equals the number of protons, so the positive and negative charges balance and the atom has no overall charge. Most of the atom's mass is in the nucleus, while most of its volume is the space occupied by electrons.
For example: A carbon atom has six protons and six neutrons in its nucleus, with six electrons around it.
What earns the marks
- States that the nucleus is at the centre of the atom and is positively charged.
- Identifies that the nucleus contains protons, which are positive, and neutrons, which are neutral.
- States that electrons are negatively charged and surround the nucleus.
- Explains that in a neutral atom the number of electrons equals the number of protons, so the charges balance.
- Recognises that most of the atom's mass is in the nucleus while most of its volume is the region occupied by electrons.
Common mistakes and how to put them right
Saying the nucleus is negatively charged.
Put it right: It is positive because of the protons, while neutrons are neutral.
Placing electrons inside the nucleus.
Put it right: Electrons occupy energy levels or shells around the nucleus.
Forgetting that neutrons have no charge and treating them as positive particles like protons.
Exam tips
- Sketch a simple labelled diagram showing the nucleus with protons and neutrons and electrons in shells around it.
- When explaining why an atom is neutral, state clearly that the number of protons equals the number of electrons.
- Use the words proton, neutron and electron accurately, and give the charge of each particle.
Try the lesson
The start of the The structure of an atom: The basic structure of an atom is a positively charged nucleus composed of both protons and neutrons surrounded by negatively charged electrons. lesson, made from checked teaching notes for this specification point.
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Which particles are found in the nucleus of an atom?
Listen
An atom has a tiny central nucleus carrying positive charge because it contains protons, which are positively charged, and neutrons, which have no charge. The nucleus therefore has a positive overall charge equal to the number of protons. Surrounding the nucleus are negatively charged electrons, arranged in energy levels or shells. In a neutral atom the number of electrons equals the number of protons, so the positive and negative charges balance and the atom has no overall charge. Most of the atom's mass is in the nucleus, while most of its volume is the space occupied by electrons. For example, a carbon atom has six protons and six neutrons in its nucleus, with six electrons around it. A strong answer earns marks for these points. States that the nucleus is at the centre of the atom and is positively charged. Identifies that the nucleus contains protons, which are positive, and neutrons, which are neutral. States that electrons are negatively charged and surround the nucleus. Explains that in a neutral atom the number of electrons equals the number of protons, so the charges balance. Exam tip: Sketch a simple labelled diagram showing the nucleus with protons and neutrons and electrons in shells around it.
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Key words
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Structure of the atom
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Charge and neutrality
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Mass distribution in the atom
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Protons, neutrons and electrons as sub-atomic particles
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See every definition
- Structure of the atom
- A positively charged nucleus composed of both protons and neutrons, surrounded by negatively charged electrons.
- Charge and neutrality
- In a neutral atom the number of electrons equals the number of protons, so the positive and negative charges balance and there is no overall charge.
- Mass distribution in the atom
- Most of the atom's mass is in the nucleus, while most of its volume is the space occupied by electrons.
- Protons, neutrons and electrons as sub-atomic particles
- Protons are positively charged, neutrons have no charge, and electrons are negatively charged and surround the nucleus.
Label the diagram
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1Box 1
2Box 2
3Box 3
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