Counting the number of electrons in an atom

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.

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.

Show answer

19 (±0)

Also accept: Number of electrons = 19

Common mistakes: Atomic mass used instead of atomic number

Show mark scheme and worked solution

Marking points

M1 · 1 mark · States or uses correct formula: 'number of electrons = atomic number'

M2 · 1 mark · Identifies atomic number of potassium = 19.

A1 · 1 mark · Correct final answer: 19 electrons.

Worked solution

Number of electrons in a neutral atom = atomic number