AQA · Chemistry · 8462
GCSE Chemistry (AQA): Elements, Isotopes & Relative Atomic Mass
Topic 1 — Atomic Structure & the Periodic Table. Generated from the caption track of Cognito's lesson video "GCSE Chemistry - Elements, Isotopes & Relative Atomic Mass (2027/28 exams)"; each card deep-links to the moment in the video it came from. Lesson 1.02 of Cognito's AQA GCSE Combined Science (Trilogy) and Chemistry course (Higher tier), filed under AQA Chemistry 8462. Teaching by Cognito — https://cognitoedu.org/coursesubtopic/c2-gcse-aqa-h-c_1.02.
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Which element has an atomic number of 3?
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Lithium (Li).
Why do isotopes of an element react chemically in the same way?
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They differ only in neutron number; their proton and electron arrangements are identical, and chemistry depends on electrons.
Define isotopes.
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Different forms of the same element that have the same number of protons but a different number of neutrons.
Relative atomic mass is denoted by the symbol ?.
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Ar
What does the atomic number of an element tell you?
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The number of protons in the nucleus of each atom of that element.
State the equation for relative atomic mass.
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Ar = sum of (isotope abundance × isotope mass) ÷ sum of the abundances of all the isotopes.
How many neutrons does an atom of carbon-13 have?
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7. It has 6 protons (because it is carbon), and 13 − 6 = 7 neutrons.
The chemical symbol for sodium is ? and for iron is Fe.
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Na
What does the abundance of an isotope mean?
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How common or rare that isotope is — the percentage of an element's atoms that are that isotope.
What is relative atomic mass?
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The average mass of the atoms of an element, taking into account the masses and abundances of all its isotopes.
Calculate the relative atomic mass of copper: Cu-63 at 69.2% and Cu-65 at 30.8% (1 d.p.).
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63.6. (69.2×63 + 30.8×65) ÷ 100 = 6361.6 ÷ 100 = 63.616.
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