Nuclear equations.pptx

AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Nuclear equations

Atomic structure

Lesson 5 of 10

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Warm-up

Atomic structure

Lesson 5 of 10

Answer each one, then check.

1

What is the mass number?

2

What is an alpha particle?

3

What is a beta particle?

4

What is the atomic number?

5

Does gamma change the nucleus's mass or charge?

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Warm-up - Answers

Atomic structure

Lesson 5 of 10

1

What is the mass number?

Protons plus neutrons

2

What is an alpha particle?

Two protons and two neutrons

3

What is a beta particle?

A fast electron from the nucleus

4

What is the atomic number?

Number of protons

5

Does gamma change the nucleus's mass or charge?

No

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Learning Objectives

Atomic structure

Lesson 5 of 10

1

Use the symbols for common nuclei and particles.

2

Balance mass numbers and atomic numbers in alpha and beta decay equations.

3

Describe the effect of alpha, beta and gamma emission on the nucleus.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Atomic structure

Lesson 5 of 10

NUCLEAR EQUATIONS

Alpha: ⁴₂He. Beta: ⁰₋₁e. In a balanced nuclear equation the mass numbers and the atomic numbers are the same on both sides.

Alpha decay: mass number falls by 4, atomic number falls by 2. Beta decay: mass number unchanged, atomic number rises by 1. Gamma: no change to mass or charge.

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Alpha and Beta Decay Equations

Atomic structure

Lesson 5 of 10

Add up the top numbers and the bottom numbers on each side.

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Effects on the Nucleus

Atomic structure

Lesson 5 of 10

How the numbers change.

Emission

Mass number

Atomic number

Alpha (α)

Decreases by 4

Decreases by 2

Beta (β)

Stays the same

Increases by 1

Gamma (γ)

Stays the same

Stays the same

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Alpha Decay

Atomic structure

Lesson 5 of 10

Radium-226 (²²⁶₈₈Ra) decays by alpha emission. Complete: ²²⁶₈₈Ra → ^A_ZRn + ⁴₂He

1

Mass numbers

226 = A + 4, so A = 222

2

Atomic numbers

88 = Z + 2, so Z = 86

ANSWER

²²⁶₈₈Ra → ²²²₈₆Rn + ⁴₂He

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Beta Decay

Atomic structure

Lesson 5 of 10

Carbon-14 decays by beta emission. Complete: ¹⁴₆C → ¹⁴_ZN + ⁰₋₁e

1

Mass numbers

14 = 14 + 0, so balanced

2

Atomic numbers

6 = Z + (−1), so Z = 7

ANSWER

¹⁴₆C → ¹⁴₇N + ⁰₋₁e

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Why It Works

Atomic structure

Lesson 5 of 10

Understand the changes.

Alpha

Two protons and two neutrons leave the nucleus.

Beta

A neutron turns into a proton and a fast electron is emitted.

Gamma

The nucleus loses energy only.

Checking

Add up the top numbers, then the bottom numbers, on each side.

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Key Terms

Atomic structure

Lesson 5 of 10

Nuclear equation

An equation showing what happens to a nucleus in radioactive decay.

Balanced

The same mass number total and atomic number total on both sides.

Daughter nucleus

The nucleus formed after decay.

Alpha decay

Emission of a helium nucleus.

Beta decay

A neutron changes to a proton and an electron is emitted.

Gamma emission

Release of energy from the nucleus as electromagnetic radiation.

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AQA GCSE PHYSICS · PAPER 1 · FOUNDATION & HIGHER

Atomic structure

Lesson 5 of 10

YOUR TASK

Balance the Equation

12 minutes

Complete: (a) ²³⁸₉₂U → ^A_ZTh + ⁴₂He (b) ⁹⁰₃₈Sr → ⁹⁰_ZY + ⁰₋₁e

1

Balance the top numbers.

2

Balance the bottom numbers.

WHAT A GOOD ANSWER SHOWS

(a) A = 234, Z = 90. (b) Z = 39.

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Can I...?

Atomic structure

Lesson 5 of 10

Write the symbol for alpha.

Write the symbol for beta.

Balance mass numbers.

Balance atomic numbers.

Complete an alpha decay equation.

Complete a beta decay equation.

State the effect of gamma emission.

Explain beta decay.

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Summary & Exam Focus

Alpha decay: mass −4, atomic −2.

Beta decay: mass unchanged, atomic +1.

Gamma: no change.

Balance both rows of numbers.

EXAM FOCUS

Complete ²²⁶₈₈Ra → ^A_ZRn + ⁴₂He. (2 marks)

Balance the top and bottom numbers.

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