CIE A Level Chemistry

Revision Notes

Syllabus Edition

First teaching 2020

Last exams 2024

|

1.1.2 Mass, Charge & Subatomic Particles

Test Yourself

Mass & Charge Distribution

  • The mass of an atom is concentrated in the nucleus, because the nucleus contains the heaviest subatomic particles (the neutrons and protons)
    • The mass of the electron is negligible

  • The nucleus is also positively charged due to the protons
  • Electrons orbit the nucleus of the atom, contributing very little to its overall mass, but creating a ‘cloud’ of negative charge
  • The electrostatic attraction between the positive nucleus and negatively charged electrons orbiting around it is what holds an atom together

Atomic Structure Mass and Charge Distribution, downloadable AS & A Level Chemistry revision notes

The mass of the atom is concentrated in the positively charged nucleus which is attracted to the negatively charged electrons orbiting around it

Behaviour of Subatomic Particles in an Electric Field

  • Protons, neutrons and electrons behave differently when they move at the same velocity in an electric field
  • When a beam of electrons is fired past the electrically charged plates, the electrons are deflected very easily away from the negative plate towards the positive plate
    • This proves that the electrons are negatively charged; like charges repel each other
    • It also shows that electrons have a very small mass, as they are easily deflected

  • A beam of protons is deflected away from the positive plate and towards the negative plate
    • This proves that the proton is positively charged
    • As protons are deflected less than electrons, this also shows that protons are heavier than electrons

  • A beam of neutrons is not deflected at all
    • Which proves that the particle is neutral in character; it is not attracted to, or repelled by, the negative or positive plate

Atomic Structure Behaviour of Particles in an Electric Field, downloadable AS & A Level Chemistry revision notes

The lighter electrons undergo much more deflection than the protons

You've read 0 of your 0 free revision notes

Get unlimited access

to absolutely everything:

  • Downloadable PDFs
  • Unlimited Revision Notes
  • Topic Questions
  • Past Papers
  • Model Answers
  • Videos (Maths and Science)

Join the 80,663 Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Francesca

Author: Francesca

Fran studied for a BSc in Chemistry with Forensic Science, and since graduating taught A level Chemistry in the UK for over 11 years. She studied for an MBA in Senior Leadership, and has held a number of roles during her time in Education, including Head of Chemistry, Head of Science and most recently as an Assistant Headteacher. In this role, she used her passion for education to drive improvement and success for staff and students across a number of subjects in addition to Science, supporting them to achieve their full potential. Fran has co-written Science textbooks, delivered CPD for teachers, and worked as an examiner for a number of UK exam boards.