Counting the number of electrons in an atom

2 marks · Easy

Show how you would calculate the number of electrons in a neutral atom of argon, given its atomic number is 18.

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

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Must show: States or uses correct relationship (electrons = atomic number), Gives correct answer

Common mistakes: Incorrectly using atomic mass

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Marking points

M1 · 1 mark · States or uses relationship: number of electrons = atomic number for a neutral atom.

A1 · 1 mark · Gives correct final answer: 18 electrons.

Worked solution

For a neutral atom, number of electrons = atomic number.

So, a neutral atom of argon has 18 electrons.