levo
Get notified

Probing Deep Into Matter

Conservation laws and nuclear equations

  • 3 things to know
  • Components 01, 02 and 03

Overview

Recall questions on the quantities that must balance, how alpha, beta and gamma emission change a nucleus, decay equations, annihilation and pair production, and why a further particle was proposed.

What you need to know

Answer each one before you reveal it.

Your recallNot started
Key term

Check that lepton number is conserved in the decay of a free neutron into a proton, an electron and an electron antineutrino.

Key term

Name three quantities that must balance on both sides of a nuclear equation.

Key term

What happens to the proton number and nucleon number of a nucleus when it emits an alpha particle?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Name three quantities that must balance on both sides of a nuclear equation.

    Model answer

    Mass and energy taken together, electric charge, and lepton number must all be conserved.

  2. 2

    What happens to the proton number and nucleon number of a nucleus when it emits an alpha particle?

    Model answer

    The proton number falls by 2 and the nucleon number falls by 4.

  3. 3

    Write the equation for the alpha decay of uranium-238.

    Model answer

    ²³⁸₉₂U → ²³⁴₉₀Th + ⁴₂He, so the product is thorium-234.

  4. 4

    What happens to the proton number and nucleon number of a nucleus when it emits a beta-minus particle?

    Model answer

    The proton number rises by 1 while the nucleon number is unchanged, because a neutron has become a proton.

  5. 5

    Write the equation for the beta-minus decay of carbon-14.

    Model answer

    ¹⁴₆C → ¹⁴₇N + ⁰₋₁e + ν̄ₑ, so the product is nitrogen-14 together with an electron and an electron antineutrino.

  6. 6

    Why must an antineutrino be included in the equation for beta-minus decay?

    Model answer

    It is needed to conserve lepton number, since the electron created has lepton number +1 and nothing else on that side would balance it, and it also carries away the missing share of the energy.

See the rest and revise

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book
2Open book
3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Planning
Implementing
Analysis
Evaluation

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

The two charges .
attractrepelcombine

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

AThe neutron has lepton number 0.
BOn the other side the proton has 0.
CThe electron has +1 and the antineutrino has −1.

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

There are 2π rad in a full circle.
TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Probing Deep Into Matter, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

Start revising, £5 a monthSee how the method works

Or £46 a year, about £3.83 a month. Cancel anytime.