The periodic table
3 marks · NormalAn 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