The structure of an atom.pptx

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

The structure of an atom

Atomic structure

Lesson 1 of 10

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Warm-up

Atomic structure

Lesson 1 of 10

Answer each one, then check.

1

What is an atom?

2

What charge does an electron have?

3

What charge does a proton have?

4

What is standard form?

5

What is electromagnetic radiation?

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Warm-up - Answers

Atomic structure

Lesson 1 of 10

1

What is an atom?

The smallest part of an element that can exist

2

What charge does an electron have?

Negative

3

What charge does a proton have?

Positive

4

What is standard form?

A number written as a × 10ⁿ

5

What is electromagnetic radiation?

Waves such as light and X-rays

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Learning Objectives

Atomic structure

Lesson 1 of 10

1

Describe the basic structure of an atom.

2

Recall the size of an atom and how it compares with the size of a nucleus.

3

State the relative charge and mass of protons, neutrons and electrons.

4

Explain how electrons change energy levels by absorbing or emitting electromagnetic radiation.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Atomic structure

Lesson 1 of 10

THE ATOM

Atoms have a radius of about 1 × 10⁻¹⁰ m. The nucleus has a radius of less than 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).

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Inside an Atom

Atomic structure

Lesson 1 of 10

The nucleus is tiny compared with the whole atom.

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Particles in an Atom

Atomic structure

Lesson 1 of 10

Learn the relative charge and mass.

Particle

Relative charge

Relative mass

Where

Proton

+1

1

Nucleus

Neutron

0

1

Nucleus

Electron

−1

Very small (about 1/2000)

Energy levels around the nucleus

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Size of the Nucleus

Atomic structure

Lesson 1 of 10

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.

1

Divide

(1 × 10⁻¹⁰)/(10 000)

2

Write 10 000 as a power of ten

10 000 = 1 × 10⁴

3

Answer

1 × 10⁻¹⁴ m

ANSWER

The nucleus has a radius of less than 1 × 10⁻¹⁴ m.

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Electron Energy Levels

Atomic structure

Lesson 1 of 10

Describe what happens when an electron absorbs electromagnetic radiation.

1

Energy

The electron gains energy from the radiation

2

Movement

It moves to a higher energy level, further from the nucleus

3

Reverse

If it emits radiation it falls to a lower energy level, closer to the nucleus

ANSWER

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

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Key Facts

Atomic structure

Lesson 1 of 10

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.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Key Terms

Atomic structure

Lesson 1 of 10

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.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Atomic structure

Lesson 1 of 10

YOUR TASK

Atom Sizes

10 minutes

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.

WHAT A GOOD ANSWER SHOWS

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

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Can I...?

Atomic structure

Lesson 1 of 10

Describe the parts of an atom.

Give the size of an atom.

Compare atom and nucleus sizes.

State charges and masses.

Explain why atoms are neutral.

Describe electron energy levels.

Say what happens when radiation is absorbed.

Use standard form.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

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)

Nucleus with protons and neutrons; electrons around it.

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