The periodic table

3 marks · Normal

An atom of zirconium has an atomic number of 40 and a mass number of 91.

Calculate the numbers of protons, neutrons, and electrons in this atom. 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

Protons = 40, Neutrons = 51, Electrons = 40

Also accept: Protons: 40, Neutrons: 51, Electrons: 40

Common mistakes: Number of neutrons = atomic number - mass number

Show mark scheme and worked solution

Marking points

M1 · 1 mark · States correct number of protons (40)

A1 · 1 mark · Correctly calculates number of neutrons (91 - 40 = 51)

B1 · 1 mark · States correct number of electrons (40) for a neutral atom

Worked solution

Number of protons = atomic number = 40

Number of electrons (in a neutral atom) = number of protons = 40