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Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section

Counting the number of electrons in an atom

21 practice questions

Start practising (10 questions)

Practice questions

1–10 of 10 · Normal

  1. Question 1

    2 marks · Normal

    State the number of electrons in:

    (a)

    an atom of magnesium (atomic number = 12)

    [1 mark]
    (b)

    an atom of phosphorus (atomic number = 15)

    [1 mark]
    Answer and see the solution →

  2. Question 2

    4 marks · Normal

    The following information is given about three atoms:

    Data about three atoms
    AtomAtomic number
    A6
    B18
    C2
    (a)

    State the number of electrons in atom A.

    [1 mark]
    (b)

    State the number of electrons in atom B.

    [1 mark]
    (c)

    State the number of electrons in atom C.

    [1 mark]
    (d)

    Explain why the number of protons is equal to the number of electrons in a neutral atom.

    [1 mark]
    Answer and see the solution →

  3. Question 3

    3 marks · Normal

    Potassium is a metal with an atomic number of 19.

    Calculate the number of electrons in a neutral atom of potassium. Show your working.

    Answer and see the solution →

  4. Question 4

    4 marks · Normal

    The table shows the atomic numbers of four elements.

    Atomic numbers of elements
    ElementAtomic number
    Fluorine9
    Neon10
    Sodium11
    Aluminium13
    (a)

    Which element in the table has 13 electrons in its atom? Give its name.

    [1 mark]
    (b)

    Which of these elements has 9 electrons in its atom? Give its name.

    [1 mark]
    (c)

    Explain why the number of electrons in a neutral atom is the same as its atomic number.

    [2 marks]
    Answer and see the solution →

  5. Question 5

    1 mark · Normal

    Which statement is correct for a neutral atom of sulfur (atomic number 16)?

    1. A.It has 8 electrons.
    2. B.It has 16 electrons.
    3. C.It has 32 electrons.
    4. D.It has 16 protons and 8 electrons.
    Answer and check →

  6. Question 6

    2 marks · Normal

    Give the number of electrons in each of the following neutral atoms:

    (a)

    Chlorine (atomic number = 17)

    [1 mark]
    (b)

    Argon (atomic number = 18)

    [1 mark]
    Answer and see the solution →

  7. Question 7

    4 marks · Normal

    The table below lists the names and atomic numbers of four different elements.

    Elements and their atomic numbers
    ElementAtomic number
    Carbon6
    Oxygen8
    Sodium11
    Chlorine17
    (a)

    Write down the number of electrons in a neutral atom of oxygen.

    [1 mark]
    (b)

    Write down the number of electrons in a neutral atom of sodium.

    [1 mark]
    (c)

    Write down the number of electrons in a neutral atom of chlorine.

    [1 mark]
    (d)

    Explain why the number of electrons is the same as the atomic number in a neutral atom.

    [1 mark]
    Answer and see the solution →

  8. Question 8

    2 marks · Normal

    State the number of electrons in a neutral atom of fluorine, which has an atomic number of 9. Give your answer with a reason.

    Answer and see the solution →

  9. Question 9

    4 marks · Normal

    A student is studying atoms of three elements: Element X, Element Y, and Element Z.

    Atomic numbers of three elements.
    ElementAtomic number
    X5
    Y12
    Z8
    (a)

    State the number of electrons in a neutral atom of element X.

    [1 mark]
    (b)

    Explain why the number of electrons in a neutral atom of element Y is 12.

    [2 marks]
    (c)

    Calculate the total number of electrons in 2 neutral atoms of element Z.

    [1 mark]
    Answer and see the solution →

  10. Question 10

    3 marks · Normal

    Calculate the number of electrons in a sample containing 5 neutral atoms of beryllium. Atomic number of beryllium = 4. Show your working.

    Answer and see the solution →