OpenRevise GCSE

Viewing as

Student Teacher

Teaching this? The teacher view adds 2 files, the mark schemes and the model answers.

Physics · Atomic structure

The structure of an atom

Describe the nuclear model of the atom: the size of atoms and nuclei, protons, neutrons and electrons, and electron energy levels.

  • 6 key terms
  • All boards
Download the full pack · 3 files

Warm-up

Answer each one, then check.

  1. 1

    What is an atom?

    Show answerHide answer

    The smallest part of an element that can exist

  2. 2

    What charge does an electron have?

    Show answerHide answer

    Negative

  3. 3

    What charge does a proton have?

    Show answerHide answer

    Positive

  4. 4

    What is standard form?

    Show answerHide answer

    A number written as \(a \times 10^n\)

  5. 5

    What is electromagnetic radiation?

    Show answerHide answer

    Waves such as light and X-rays

Learning Objectives

  1. 1Describe the basic structure of an atom.
  2. 2Recall the size of an atom and how it compares with the size of a nucleus.
  3. 3State the relative charge and mass of protons, neutrons and electrons.
  4. 4Explain how electrons change energy levels by absorbing or emitting electromagnetic radiation.

THE ATOM

Atoms have a radius of about \(1 \times 10^{-10}\) m. The nucleus has a radius of less than \(\tfrac{1}{10\,000}\) of the atom's radius but contains most of the mass.

The nucleus is positively charged (protons and neutrons) and is surrounded by negatively charged electrons at different distances (energy levels).

Particles in an Atom

Learn the relative charge and mass.

  • Proton

    Relative charge: +1. Relative mass: 1. Where: Nucleus

  • Neutron

    Relative charge: 0. Relative mass: 1. Where: Nucleus

  • Electron

    Relative charge: −1. Relative mass: Very small (about 1/2000). Where: Energy levels around the nucleus

Size of the Nucleus

The radius of an atom is about 1 × 10⁻¹⁰ m. The radius of its nucleus is less than 1/10 000 of this. Calculate the largest possible radius of the nucleus.

Show the solutionHide the solution
  1. 1 Divide \(\dfrac{1 \times 10^{-10}}{10\,000}\)
  2. 2 Write 10 000 as a power of ten \(10\,000 = 1 \times 10^{4}\)
  3. 3 Answer \(1 \times 10^{-14}\) m

AnswerThe nucleus has a radius of less than \(1 \times 10^{-14}\) m.

Electron Energy Levels

Describe what happens when an electron absorbs electromagnetic radiation.

Show the solutionHide the solution
  1. 1 Energy The electron gains energy from the radiation
  2. 2 Movement It moves to a higher energy level, further from the nucleus
  3. 3 Reverse If it emits radiation it falls to a lower energy level, closer to the nucleus

AnswerAbsorbing radiation moves an electron further from the nucleus; emitting radiation moves it closer.

Key Facts

Points examiners ask about.

  • Neutral atoms

    The number of electrons equals the number of protons, so there is no overall charge.

  • Mass

    Most of the mass of an atom is in the nucleus.

  • Space

    Most of an atom is empty space.

  • Positive ions

    An atom that loses one or more outer electrons becomes a positive ion.

Atom Sizes

An atom has a radius of 1 × 10⁻¹⁰ m and a nucleus of radius 1 × 10⁻¹⁵ m. How many times larger is the atom's radius than the nucleus's radius? Where is most of the mass?

1. Divide the two radii.

2. Use powers of ten.

A good answer shows: The atom is 100 000 times larger (10⁻¹⁰ ÷ 10⁻¹⁵ = 10⁵). Most of the mass is in the nucleus.

Can I...?

  1. 1Describe the parts of an atom.
  2. 2Give the size of an atom.
  3. 3Compare atom and nucleus sizes.
  4. 4State charges and masses.
  5. 5Explain why atoms are neutral.
  6. 6Describe electron energy levels.
  7. 7Say what happens when radiation is absorbed.
  8. 8Use standard form.

Summary & Exam Focus

  • Atoms are about 1 × 10⁻¹⁰ m in radius.
  • The nucleus is less than 1/10 000 of the atom's radius.
  • Protons +1, neutrons 0, electrons −1.
  • Electrons move to higher levels by absorbing radiation.

Exam focus

Describe the structure of an atom. (3 marks) (3 marks)

Nucleus with protons and neutrons; electrons around it.

Key terms

The vocabulary this lesson expects you to use. Each one is linked from the first place it appears above.

Atom
The smallest part of an element that can exist.
Nucleus
The positively charged centre of an atom containing protons and neutrons.
Proton
A positive particle in the nucleus.
Neutron
A neutral particle in the nucleus.
Electron
A negative particle that orbits the nucleus.
Energy level
A distance from the nucleus at which an electron can be.

Practice questions

Have a go at each one before you open its answer.

  1. Question 1 Describe 3 marks

    Describe the structure of an atom.

    Show answerHide answer

    Model answer

    A small central nucleus containing protons and neutrons, with electrons arranged at different distances (energy levels) from the nucleus.

    Mark scheme

    • Small central nucleus — 1 mark
    • Nucleus contains protons and neutrons — 1 mark
    • Electrons around the nucleus — 1 mark
  2. Question 2 Complete 3 marks

    Complete the table to show the relative charge of a proton, a neutron and an electron.

    Show answerHide answer

    Model answer

    Proton +1; neutron 0; electron −1.

    Mark scheme

    • +1 — 1 mark
    • 0 — 1 mark
    • −1 — 1 mark
  3. Question 3 Calculate 3 marks

    The radius of an atom is 1 × 10⁻¹⁰ m. The radius of its nucleus is less than 1/10 000 of the radius of the atom. Calculate the largest possible radius of the nucleus. Give your answer in standard form.

    Show answerHide answer

    Model answer

    \(1 \times 10^{-10} \div 10\,000 = 1 \times 10^{-14}\) m

    Mark scheme

    • Divides by 10 000 — 1 mark
    • Correct power — 1 mark
    • 1 × 10⁻¹⁴ m — 1 mark
  4. Question 4 Explain 2 marks

    An atom has no overall electrical charge. Explain why.

    Show answerHide answer

    Model answer

    The number of electrons is equal to the number of protons, so the negative and positive charges cancel.

    Mark scheme

    • Number of electrons equals number of protons — 1 mark
    • Charges cancel — 1 mark
  5. Question 5 Explain 3 marks

    An electron in an atom absorbs electromagnetic radiation. Describe what happens to the electron. Then say what happens when the electron emits radiation.

    Show answerHide answer

    Model answer

    It moves to a higher energy level, further from the nucleus. When it emits radiation it moves to a lower energy level, closer to the nucleus.

    Mark scheme

    • Absorbs radiation: moves to higher energy level or further from nucleus — 1 mark
    • Emits radiation: moves to lower energy level — 1 mark
    • Closer to the nucleus — 1 mark

Quick check

  1. The nucleus contains...

    1. Aelectrons and protons
    2. Bprotons and neutrons
    3. Celectrons only
    4. Dneutrons and electrons
    Show answerHide answer

    B: protons and neutrons

    Electrons are outside the nucleus.

  2. The charge on a neutron is...

    1. A+1
    2. B−1
    3. Czero
    4. D+2
    Show answerHide answer

    C: zero

    Neutrons are neutral.

  3. Most of the mass of an atom is in the...

    1. Aelectrons
    2. Bspace around
    3. Couter shell
    4. Dnucleus
    Show answerHide answer

    D: nucleus

    Protons and neutrons are heavy.

  4. An atom loses an electron. It becomes a...

    1. Apositive ion
    2. Bnegative ion
    3. Cneutral atom
    4. Dneutron
    Show answerHide answer

    A: positive ion

    It has more protons than electrons.

  5. The radius of an atom is about...

    1. A1 × 10⁻² m
    2. B1 × 10⁻¹⁰ m
    3. C1 × 10⁻¹⁵ m
    4. D1 m
    Show answerHide answer

    B: 1 × 10⁻¹⁰ m

    About 0.1 nanometres.

Downloads

Free to keep, print and annotate.

Download all 3 as a zip
Something here looks wrong?

Tell us what and we will go and look. It goes to whoever writes these pages, nobody else, and we do not ask who you are — so there is nothing to sign and nothing comes back to you.