Solutions: Atomic Structure
Q4.
An atom of argon
is ionised by the removal of two orbiting electrons.
(a) How many protons and neutrons are there in this ion?
18 protons ![](../../../../graphics/symbols/nuclides/ticksmall.png)
(37 - 18 gives) 19 neutrons ![](../../../../graphics/symbols/nuclides/ticksmall.png)
(2 marks)
(b) What is the charge, in C, of this ion?
Two electrons have been removed so the charge is positive
Q = 2 x 1.6 x 10-19 C
Q = 3.2 x 10-19 C ![](../../../../graphics/symbols/nuclides/ticksmall.png)
(2 marks)
(c) Which constituent particle of this ion has:
(i) a zero charge per unit mass ratio,
neutron ![](../../../../graphics/symbols/nuclides/ticksmall.png)
(ii) the largest charge per unit mass ratio?
electron ![](../../../../graphics/symbols/nuclides/ticksmall.png)
(2 marks)
(d) Calculate the percentage of the total mass of this ion that is accounted for by the mass of its electrons.
ratio = (16 x 9.11 x 10-31
)/(37 x 1.67 x 10-27
)
ratio = 2.36 x 10-4
percentage = 2.36 x 10-2 %
(3 marks)
(Total 9 marks)