Level Chemistry Transition Unit Worksheet With Answer Key - Healthcote School Page 3
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172
The structure of atoms
Task 1:
1 Complete the spaces to create a set of notes about the structure of atoms.
Atoms consist of a central
nucleus
containing protons and neutrons. The nucleus is
small
compared to the size of the whole atom. The nucleus is surrounded by
electrons
in energy levels
(also called shells). Atoms have no electric charge because they contain the same number of
protons and electrons.
Sub-atomic
Relative mass
Relative charge
particle
Proton
1
+1
Neutron
1
0
Electron
Almost zero
-1
Electrons in
Atomic number = number of protons.
Mass number = number of
protons
+ number of neutrons.
mass number
19
Symbol
e.g.
F
atomic number
9
protons =
9
neutrons =
10
electrons =
9
Atoms of the same element have the same number of protons. It is the number of
protons
that
determines what type of atom it is (e.g. all atoms with six protons are carbon atoms). Atoms of
different elements have different numbers of protons. Isotopes are atoms of the same element.
They contain the same number of
protons
but a different number of neutrons.
2 Complete the table about some atoms.
Atom
Atomic
Mass number Number of
Number of
Number of
number
protons
neutrons
electrons
23
Na
11
11
23
11
12
11
Li
3
7
3
4
3
Ar
18
40
18
22
18
K
19
39
19
20
19
Al
13
27
13
14
13
Cl
17
35
17
18
17
235
U
92
235
92
143
92
92
238
U
92
238
92
146
92
92
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