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Radioactivity

Relative masses and charges of subatomic particles

  • 3 things to know
  • Paper 5

Overview

Relative masses and charges of the proton, neutron, electron and positron, why electrons add almost no mass, why a complete atom is neutral, matching numbers of protons and electrons, and how an extra electron makes a negative ion.

What you need to know

Answer each one before you reveal it.

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Key term

State the relative mass and the relative charge of a proton.

Key term

State the relative mass and the relative charge of a neutron.

Numbers

State the relative mass and the relative charge of an electron.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    State the relative mass and the relative charge of a proton.

    Model answer

    A proton has a relative mass of 1 and a relative charge of +1.

  2. 2

    State the relative mass and the relative charge of a neutron.

    Model answer

    A neutron has a relative mass of 1 and a relative charge of 0.

  3. 3

    State the relative mass and the relative charge of an electron.

    Model answer

    An electron has a relative mass of about 1/1836 and a relative charge of −1.

  4. 4

    State the relative mass and the relative charge of a positron.

    Model answer

    A positron has a relative mass of about 1/1836 and a relative charge of +1.

  5. 5

    How does a positron compare with an electron?

    Model answer

    A positron has the same tiny mass as an electron but the opposite, positive charge.

  6. 6

    Which of the proton, the neutron and the electron has by far the smallest mass?

    Model answer

    The electron, whose mass is only about 1/1836 that of a proton.

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