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Atomic radius is the distance from the centre of an atom's nucleus to its outer electron shell, approximately 0.1 nm or 1 × 10⁻¹⁰ m. Free notes and FAQs.
The Size and Scale of Atoms is part of A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes in GCSE Edexcel Higher Chemistry.
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Atomic radius is the distance from the centre of an atom's nucleus to its outer electron shell, approximately 0.1 nm or 1 × 10⁻¹⁰ m. Free notes and FAQs.
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Use this lesson to stay inside A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes while connecting the detail back to the wider Topic 1: Key concepts in chemistry topic.
Read the core explanations from The Size and Scale of Atoms before testing yourself from memory.
Everything you touch is made of atoms, yet you've never seen one. Why not? The answer lies in their incredible smallness - atoms are so tiny that even the most powerful microscopes struggle to show them clearly.
To understand just how small atoms are, we need to think in terms of scientific notation and compare them to objects we know. This isn't just academic curiosity - understanding atomic scale helps explain why materials behave the way they do and why certain technologies work.
Atoms have a radius of about 0.1 nanometres. That's 0.1 × 10⁻⁹ metres, or in standard form, 1 × 10⁻¹⁰ metres. This number is so small it's hard to grasp intuitively.
To put this in perspective, if you could line up atoms side by side, you'd need 10 billion of them to stretch across just one metre. That's more atoms in a metre than there are seconds in about 300 years.
If atoms are incredibly small, their nuclei are almost unimaginably tiny. The nucleus has a radius of about 1 × 10⁻¹⁴ metres - that's 10,000 times smaller than the atom itself.
Here's where it gets mind-bending: if an atom were scaled up to the size of a football stadium, the nucleus would be about the size of a marble sitting in the centre circle. The rest is mostly empty space where electrons move around.
Worked example: Calculating the Size Ratio
Calculate how many times smaller the nucleus is compared to the atom.
Answer: The atom is 10,000 times larger than its nucleus
The best way to understand atomic scale is through analogies. These comparisons help us grasp just how small atoms really are and why we can't see them with ordinary light.
If you could magnify a tennis ball to the size of Earth, the atoms in that tennis ball would be about the size of grapes. That's the scale we're dealing with - atoms are to tennis balls as grapes are to planets.
Another way to think about it: there are more atoms in a glass of water than there are glasses of water in all the world's oceans. The numbers are staggering because atoms are so incredibly small.
Understanding atomic scale isn't just about memorising numbers. It explains fundamental properties of matter and helps us understand why certain scientific techniques work.
Because atoms are smaller than visible light wavelengths, we need special techniques to study them. Electron microscopes use electron beams instead of light, while X-ray crystallography uses X-rays to determine atomic arrangements in crystals.
The tiny size of atoms also explains why materials appear continuous to us, even though they're made of discrete particles. There are so many atoms packed together that we can't detect the gaps between them.
Questions about atomic scale often test your ability to work with scientific notation and make comparisons. Here's how to tackle them successfully and avoid the most common pitfalls.
The most common mistake is confusing the size of atoms with the size of nuclei. Remember: atoms are 1 × 10⁻¹⁰ m, nuclei are 1 × 10⁻¹⁴ m. That's a factor of 10,000 difference.
Exam tip: always convert units carefully between metres, nanometres, and the scale of the nucleus before comparing sizes., always identify the key chemical idea first, then link it to evidence, data, or an equation. A high-scoring GCSE answer names the particles involved, states what changes, and justifies the conclusion using correct scientific language. Where calculations are used, show each step with units and keep significant figures sensible. Finally, check that terminology matches AQA wording so your answer is unambiguous and mark-scheme friendly.
Atoms are extremely small, and the nucleus is far smaller still. A typical atom is about 0.1 nm across, while the nucleus is about 1 × 10⁻⁵ nm across. This means most of the atom is empty space, which is one reason it is useful to compare atomic and nuclear sizes on a scale diagram.
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Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
Atomic radius is the distance from the centre of an atom's nucleus to its outer electron shell, approximately 0.1 nm or 1 × 10⁻¹⁰ m.
A nucleus is about 1 × 10⁻⁵ nm across, compared with about 0.1 nm for a typical atom. In metres, the nuclear radius is about 1 × 10⁻¹⁴ m.
Divide the atomic radius by the nuclear radius: 1 × 10⁻¹⁰ ÷ 1 × 10⁻¹⁴ = 1 × 10⁴. When dividing powers of 10, subtract the indices, so the atom is 10,000 times larger than its nucleus.
We cannot see atoms because they are smaller than visible light wavelengths. Special techniques are needed instead: electron microscopes use electron beams rather than light, and X-ray crystallography uses X-rays to determine atomic arrangements in crystals.
About 10 billion atoms lined up side by side would stretch across one metre, because atoms have a radius of about 1 × 10⁻¹⁰ m. That is more atoms than there are seconds in about 300 years.
If an atom were scaled up to the size of a football stadium, the nucleus would be about the size of a marble in the centre circle. The rest of the atom is mostly empty space where electrons move around.
Special techniques are needed to look at atoms because atoms are smaller than visible light wavelengths. Electron microscopes use electron beams instead of light, and X-ray crystallography uses X-rays to find atomic arrangements in crystals.
Materials look continuous because so many tiny atoms are packed together that the gaps between them cannot be detected. Atoms are only about 0.1 nm in radius.
0.1 nm is 0.1 × 10⁻⁹ metres, which is 1 × 10⁻¹⁰ m in standard form. This is the typical radius of an atom.
If a tennis ball were made as big as Earth, its atoms would be about the size of grapes. Atoms are to tennis balls as grapes are to planets.