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Atomic Structure

Isotopes and relative isotopic mass

  • 3 things to know
  • Unit AS 1

Overview

Term isotopes, relative isotopic mass and numbers of neutrons in the isotopes ³⁵Cl and ³⁷Cl.

What you need to know

Answer each one before you reveal it.

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Key term

Define the term isotopes.

Key term

Why do the isotopes of an element have identical chemical properties?

Key term

Give one physical property in which two isotopes of an element differ.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Define the term isotopes.

    Model answer

    Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.

  2. 2

    Why do the isotopes of an element have identical chemical properties?

    Model answer

    Chemical properties depend on the electronic configuration, and isotopes of one element have the same number and arrangement of electrons.

  3. 3

    Give one physical property in which two isotopes of an element differ.

    Model answer

    Isotopes differ in mass, so quantities such as density and rate of diffusion are slightly different.

  4. 4

    Define relative isotopic mass.

    Model answer

    Relative isotopic mass is the mass of one atom of an isotope compared with one twelfth of the mass of one atom of carbon-12.

  5. 5

    Why is relative isotopic mass very close to a whole number?

    Model answer

    Protons and neutrons each have a mass of almost exactly 1 on the carbon-12 scale, so the total is close to the number of nucleons.

  6. 6

    State the numbers of neutrons in the isotopes ³⁵Cl and ³⁷Cl.

    Model answer

    ³⁵Cl has 18 neutrons and ³⁷Cl has 20 neutrons.

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