Topic 2 Review Questions
1.
The element vanadium has two isotopes,
50
23
V and
51
23V,
and a relative atomic mass of 50.94.
(a)
Define the term isotope. (1)
(b)
State the number of protons, electrons and neutrons in
(c)
State and explain which is the more abundant isotope. (1)
(d)
State the name and the mass number of the isotope relative to which all atomic masses are
measured. (1)
50
23V. (2)
(Total 5 marks)
2.
(a)
State a physical property that is different for isotopes of an element.
(1)
(b)
Chlorine exists as two isotopes, 35Cl and 37Cl. The relative atomic mass of chlorine is
35.45. Calculate the percentage abundance of each isotope.
(2)
(Total 3 marks)
3.
(a)
A sample of argon exists as a mixture of three isotopes.
mass number 36, relative abundance 0.337%
mass number 38, relative abundance 0.0630%
mass number 40, relative abundance 99.6%
Calculate the relative atomic mass of argon.
(2)
(b)
State the number of electrons, protons and neutrons in the ion 56Fe3+.
electrons: ............................. protons: ............................. neutrons: ...........................
(2)
(Total 6 marks)
4.
The element bromine exists as the isotopes 79Br and 81Br, and has a relative atomic mass of 79.90.
(a)
Complete the following table to show the numbers of sub-atomic particles in the species
shown.
an atom of 79Br
an ion of 81Br–
protons
neutrons
electrons
(3)
1
(b)
State and explain which of the two isotopes 79Br and 81Br is more common in the element
bromine.
(1)
(c)
The element calcium is in the same period of the Periodic Table as bromine.
Write the electron configuration for an atom of calcium.
(1)
(Total 5 marks)
5.
(a)
List the following types of electromagnetic radiation in order of increasing wavelength
(shortest first).
I.
Yellow light
II.
Red light
III.
Infrared radiation
IV.
Ultraviolet radiation
(1)
(b)
Distinguish between a continuous spectrum and a line spectrum.
(1)
(c)
The thinning of the ozone layer increases the amount of UV-B radiation that reaches the
Earth’s surface.
Type of Radiation
Wavelength / nm
UV-A
320–380
UV-B
290–320
Based on the information in the table above explain why UV-B rays are more dangerous
than UV-A.
(3)
(Total 5 marks)
6.
State the number of protons, electrons and neutrons in the ion
15
7
N3–.
(Total 2 marks)
2
7.
A sample of germanium is analysed in a mass spectrometer. The first and last processes in mass
spectrometry are vaporization and detection.
The sample of germanium is found to have the following composition:
Isotope
Relative abundance / 
(i)
70
Ge
22.60
72
Ge
25.45
74
Ge
36.73
76
Ge
15.22
Define the term relative atomic mass.
(2)
(ii)
Calculate the relative atomic mass of this sample of germanium, giving your answer
to two decimal places.
(2)
(Total 9 marks)
8.
State the electron configurations of the following species:
Si
P3–
(Total 2 marks)
9.
Identify the numbers of protons, neutrons and electrons in the species 33S2–.
(Total 1 mark)
10.
Determine the full electron configuration of an atom of an Fe3+.
(Total 1 mark)
ANSWERS: Topic 2 Review Questions Mark Scheme
1)
(a)
(b)
(c)
(d)
atom of same element/same number of protons but with different
mass number/number of neutrons;
protons
electrons
neutrons
51
23
23
23
27
Three correct [2], two correct [1].
V /51 nearer to Ar value of 50.94;
carbon, 12/12C;
1
2
1
1
3
2)
(a)
(b)
mass/density/for gases: rate of effusion or diffusion/melting point/
boiling point
Do not accept mass number.
if 35Cl = x, then (x = 35.00) + (1 – x) 37.00 = 35.45
Award [1] for set up.
therefore, x = 0.775;
35
Cl = 77.5% and 37Cl = 22.5%;
(need both for mark);
3)
(a)
(b)
4)
1
2
relative atomic mass = 36  0.337  38  0.0630  40  99.6 ;
100
23 electrons;
26 protons;
30 neutrons;
Award [2] for three correct, [1] for two correct.
2
2
(a)
an atom of 79Br
an ion of 81Br–
protons
35
35
;
neutrons
44
46
;
electrons
35
36
;
3
5)
(b)
79
(c)
1s22s22p63s23p64s2
1
(a)
IV < I < II < III/
ultra violet radiation < yellow light < red light < infrared radiation;
1
(b)
(c)
Br because Ar is closer to 79/OWTTE;
1
A continuous spectrum has all wavelengths/frequencies whereas
a line spectrum has only shows lines representing specific wavelengths/frequencies;
UV-B radiation has shorter wavelength;
hence, has higher energy;
increases risk of damage to skin cells/causes cancer/cell mutations;
1
3
4
6) 7 protons, 8 neutrons, 10 electrons;
Award [2] for three correct and [1] for two correct.
7)
(i)
(ii)
average or (weighted) mean of masses of all isotopes of an element;
relative to (one atom of) 12C;
Both marks available from a suitable expression.
Si
2
Ar = (70 0.2260) + (72 0.2545) + (74 0.3673) + (76 0.1522);
= 72.89;
No other final answer acceptable.
Award [2] for correct final answer.
8)
2
2
1s22s22p63s23p2
2
P3
1s22s22p63s23p6
9) 16 protons and 17 neutrons and 18 electrons;
1
10) Fe3+: 1s22s22p63s23p63d5;
1
5