Chapter test answers
Chapter 2 It’s all elemental: What are the elements of matter?
1
A
2
B
3
D
4
A
5
D
6
B
7
A
8
B
9
A
10 C
11 D
12 A
13 C
14 A
15 B
16 B
17 B
18 B
19 B
20 B
21 The periodic table shows the metals on the left hand side and the non-metals on the right hand side. The
location of sodium on the left had side and in group 1 informs you that sodium is a metal and it has only
one valence electron in its outer shell. The location of oxygen on the right had side and in group 6 informs
you that oxygen is a non-metal and it has six valence electrons in its outer shell.
22 a
Mass number = 7 = number of protons + neutrons
Atomic number = 3 = number of protons
Therefore there must be 4 neutrons
The number of electrons = number of protons = 3
b
Mass number = 27 = number of protons + neutrons
Atomic number = 13 = number of protons
Therefore there must be 14 neutrons
The number of electrons = number of protons = 13
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23 The atomic number is the number of protons in the nucleus of an atom.
The mass number is the total number of protons plus neutrons in the nucleus of an atom.
24
•
All of the atoms of oxygen have the same atomic number = 6 = number of protons
•
Each of the atoms are different isotopes. This means that they have different numbers of neutrons in the
nucleus. The first isotope, with a mass number of 18 has 8 neutrons in the nucleus.
•
The second isotope, with mass number of 17 has 9 neutrons in the nucleus.
•
The third isotope, with mass number of 18 has ten neutrons in the nucleus.
25
element
Mass
num
ber
Atomic
num
ber
Number
of
prot
ons
Number
of
neut
rons
Number
of
elec
tron
s
Electronic
configur
ation
Sodium
23
11
11
12
11
2,8,1
Magnesium
24
12
12
12
12
2,8,2
Lithium
7
3
3
4
3
2,1
Carbon
12
6
6
6
6
2,4
26 a
Sodium bromide
b
Potassium oxide
c
Magnesium sulfide
d
Ammonium chloride
27 a
MgO
b
CaCl2
c
AgBr
d
FeCl2
28 a
metals
b
non-metals
c
noble gas
d
cation
e
anion
f
metal
g
ionic
29 They are unreactive.
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30 The non-metal could be a gas or a solid that is not shiny and may be coloured. Observation of the sample
could help to identify the non-metal.
Metals conduct electricity so an electric circuit could be created using a battery and some wires and a light
globe. Place the sample of each element in the circuit and see whether the light globe shines or not.
The metalloids may conduct electricity but it would not react with an acid. Place a small sample of the
remaining two elements into containers of vinegar and observe their reaction. The metal will become
covered in bubbles.
31
32
33 In Q31 you can see that potassium has one electron in its outer shell. This electron can be rapidly donated
to fluorine atoms to complete their outer shell (see Q32). The potassium and fluorine atoms in the gas jar
react by transferring electrons from potassium atoms to fluorine atoms and the ionic compound potassium
fluoride is formed.
Any element except for noble gases and helium. As they have to describe the reaction in the next part
34 a
of the question it is hoped that they chose a Group 1 or 2 element.
b
Element in Group 1 or 2 will donate 1 or 2 electrons to each oxygen atom to form an ionic compound.
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35 The plum pudding model was not correct. In a plum pudding the location of the fruit is random and there is
no set pattern. Two or more pieces of fruit may be packed closely together and the rest of it may be spread
throughout the pudding.
We now know that the structure of atoms does follow set patterns. The electrons are not found just
anywhere in an atom. They are located only in special regions which are called shells and these are
outside the nucleus of the atom.
36 The heat of the flame causes the electrons of the sodium or the copper ions to become excited. This
enables them to jump into outer shells where they are not usually found. However, they can only stay in
these shells for a short time before they drop back into their usual location. When they fall back to the lower
energy shell the extra energy is given out as light. Because the sodium and copper atoms have different
electronic configurations, the jumping of electrons between shells is different and this causes the light
(flame colour) to be a different colour.
37 a
LiCl
b
Li2O
38 Any two of sodium, potassium, rubidium, cesium, francium
39 We now know that statements a and b are incorrect. Atoms are made up of smaller parts – the protons,
neutrons and electrons. All atoms of an element do not have identical mass. Each isotope has a different
mass because it has a different number of neutrons in its nucleus.
40
Scientist
Contribution to ideas of atomic structure
John Thomson
Plum pudding model of the atom
Ernest Rutherford
By shooting alpha particles at thin films of gold he
identified that most of the atom is empty space
Niels Bohr
Proposed that electrons exist at precise distances from
the nucleus
Erwin Schrodinger
Proposed mathematical models to explain the behaviour
of particles inside atoms
James Chadwick
Discovered the neutron
Oxford Big Ideas Science 3
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