Counting the number of electrons in an atom

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.

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A neutral atom of fluorine has 9 electrons because the number of electrons equals the atomic number.

Also accept: 9 electrons because atomic number equals number of electrons in a neutral atom

Common mistakes: Giving atomic number only without explanation; Confusing electrons with protons

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Marking points

B1 · 1 mark · States that a neutral atom of fluorine has 9 electrons.

B1 · 1 mark · Gives correct reason that number of electrons equals the atomic number for a neutral atom.

Worked solution

The atomic number of fluorine is 9.

For a neutral atom, the number of electrons is equal to the atomic number.

Therefore, a neutral atom of fluorine has 9 electrons.