AQA · Physics · 8463

GCSE Physics: Mass number, atomic number and isotopes

Atomic structure · AQA GCSE Physics (8463), specification point 4.4.1.2. Cards are generated from the exam board's own specification for "Mass number, atomic number and isotopes", and every card links back to the page it came from. Specification © AQA — used with attribution.

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  1. In a neutral atom, the number of electrons equals the number of what?

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    Protons in the nucleus. The equal numbers of positive and negative charges cancel, so the atom has no overall charge.

  2. What is the overall electrical charge of an atom?

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    Zero — atoms have no overall charge because they contain equal numbers of protons and electrons.

  3. Define the atomic number of an element.

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    The number of protons in an atom of that element.

  4. Define the mass number of an atom.

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    The total number of protons and neutrons in the atom.

  5. All atoms of a particular element have the same number of ?.

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    protons

  6. What are isotopes?

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    Atoms of the same element (same number of protons) that have different numbers of neutrons.

  7. Which subatomic particle differs in number between isotopes of the same element?

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    Neutrons. The proton number is fixed for a given element.

  8. How do you calculate the number of neutrons in an atom?

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    Mass number minus atomic number (neutrons = protons + neutrons − protons).

  9. How does an atom become a positive ion?

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    By losing one or more of its outer electrons, leaving more protons than electrons.

  10. Atoms turn into positive ions if they lose one or more outer ?.

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    electrons

  11. Why do isotopes of an element have the same chemical identity?

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    They have the same number of protons (same atomic number), which defines the element; only the neutron count differs.

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