7.4Chapter 7: Inside Atoms

Inside sub-atomic particles — Alhussan Chemistry - Stage 8 Revision Notes & Topical Questions

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📚 Alhussan Chemistry - Stage 8 Hub / Topical Revision

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Lesson summary

7.4 Inside sub-atomic particles — Electrostatic Attraction and Atomic Structure — Alhussan International Academy — Chemistry (Stages 7–9) notes: Use electrostatic forces to explain why atoms hold together, and describe how scientists collaborate to study sub-atomic particles.Char…

Force rule
Electron attraction
Inner shells
Outer shell
Repulsion in the nucleus
Strong nuclear force

Part 1 of 8Electric charge and forces

Charges

Charges matter contains positive and negative charges.

Force rule

Force rule like charges repel and opposite charges attract.
These electrostatic forces become stronger as particles get closer together or as the charges get bigger.

Charges	Force
+ and +	Repel
- and -	Repel
+ and -	Attract

Part 2 of 8Holding the atom together

Electron attraction

Electron attraction negative electrons are attracted to the positive nucleus, which keeps them in their shells.

Inner shells

Inner shells electrons nearest the nucleus are held most strongly because they are closer.

Outer shell

Outer shell electrons are held less strongly because they are further away and partly shielded by inner electrons.
This is why outer electrons can be lost or shared in chemical reactions.

Repulsion

Repulsion electrons repel one another and protons repel one another, so a model of the atom must take this into account.

Part 3 of 8The nucleus

Repulsion in the nucleus

Repulsion in the nucleus several protons are crowded into a very small space and repel each other strongly.

Strong nuclear force

Strong nuclear force it acts between protons and neutrons at very short range and is stronger than the repulsion between protons.

Neutrons

Neutrons they help to separate protons and add to the attractive force, so heavier nuclei need more neutrons than protons.

Unstable nuclei

Unstable nuclei if the balance is wrong the nucleus is radioactive and may emit particles to become stable.

Part 4 of 8Applying atomic structure

Applying atomic structure

Group trend

Group trend in a group such as Group 1, atoms get bigger as there are more shells.
The outer electron is further away and more shielded, so it is lost more easily.
This explains why potassium is more reactive than sodium.

Period trend

Period trend across a period the nuclear charge increases while electrons are added to the same shell, so atoms become slightly smaller.

Part 5 of 8Static electricity

Charging

Charging rubbing a polythene rod with a cloth transfers electrons from the cloth to the rod.
The rod becomes negatively charged and the cloth positively charged.

Forces

Forces two rods charged in the same way repel, and a charged rod and the cloth attract.

Attracting paper

Attracting paper a charged rod attracts small pieces of paper because it shifts charge in the paper, leaving the near side with the opposite charge.

Balloon

Balloon a balloon rubbed with a cloth becomes negative and sticks to a wall by attraction to positive charges there.

Lightning

Lightning it is a huge discharge of static electricity between cloud and ground.

What moves

What moves only electrons move in these processes; protons stay in the nucleus.

Part 6 of 8Questions about sub-atomic particles

Questions about sub-atomic particles

Atom model

Atom model by 1932 scientists knew most of the mass of an atom is in its nucleus of protons and neutrons, with electrons moving outside.
A helium atom has two protons and two neutrons in its nucleus and two electrons outside.

Bose and Einstein

Satyendra Nath Bose, born in Kolkata in 1894, wrote to Albert Einstein about his ideas, and together they predicted the Bose-Einstein condensate.
This new state of matter would exist only at very low temperatures.

Higgs boson

Higgs boson in 1964 six scientists, including Peter Higgs, hypothesised a particle that gives sub-atomic particles their mass.

Part 7 of 8The Large Hadron Collider

The Large Hadron Collider

Teamwork

Teamwork thousands of scientists from more than 100 countries, each expert in different things, designed and built the Large Hadron Collider (LHC), ready by 2010.

Structure

Structure the LHC is a 27 km circular tunnel deep underground,
- where huge magnets guide beams of high-energy protons around the circle in both directions.

Collisions

Collisions the protons travel faster and faster, collide and break up, and four huge detectors follow the particles made.

Data

Data the detectors send data to hundreds of scientists in many countries, who study the evidence and may collaborate to make conclusions.

Result

Result on 4 July 2012 LHC scientists announced a new boson that behaves as a Higgs boson would, supporting the hypothesis made nearly 50 years earlier.

Future

Future the LHC will be upgraded between 2025 and 2027 so protons collide more frequently and give extra data.

Part 8 of 8Collaboration and peer review

Collaboration and peer review

Peer review

Peer review expert scientists check papers and may suggest corrections and improvements before a good paper is published in a scientific journal.

Other scientists read the paper, which may give them ideas for new investigations.

Advantages of collaboration

Advantages of collaboration people with different expertise combine skills, share costs and check each other's work.

International teams

International teams they are easier now than 100 years ago because of fast communication such as the Internet and cheap travel.

Key terms

Term	Meaning
Electrostatic force	a force between charged objects.
Shielding	reduced attraction on outer electrons caused by inner electrons.
Strong nuclear force	a short-range force holding the nucleus together.
Attract	pull together.
Repel	push apart.
Peer review	checking of scientific papers by expert scientists before publication.

Avoid these mistakes

Thinking like charges attract — like charges repel and opposite charges attract.

Saying that neutrons carry charge — neutrons are neutral.

Forgetting that electrons repel each other — they repel as well as being attracted to the nucleus.

Saying protons move when objects are charged by rubbing — only electrons transfer.

Last updated: 13 October 2026