SMART LEARNING GURU TUITION CENTRE
SECONDARY THREE CHEMISTRY
CHAPTER 5 : ATOMIC STRUCTURE
ASSIGNMENT
Name : __________________________(
Class : 3 (
)
Grade :
)
Date
/34
: ____________
Practice :
1. Complete the following table. The first one has been done for you.
Element
Proton
Number
Nucleon
Number
Number of
protons
Number of
electrons
Number of
neutrons
Lithium
Fluorine
Argon
Calcium
Sodium
2. Tungsten is used to make filaments in electric light bulbs. The chemical symbol for tungsten is
184
74
W
. How many protons, neutrons and electrons are present in one atom of tungsten?
[3]
*3. The element hydrogen has three isotopes, hydrogen, H, deuterium, D and tritium, T. The nucleon
(mass) number of the isotopes are one, two and three respectively.
Name
Hydrogen
Deuterium
Tritium
Nucleon (mass) number
protons
neutrons
(a) Complete the table to show the numbers of particles in the three nuclei.
[2]
o
o
(b) The boiling point of D2O is 101.6 C but that of H2O is 100.0 C. Suggest a reason for this
difference.
[1]
(c) Calcium reacts with cold water. Construct a balanced chemical equation for the reaction between
D2O and calcium.
[1]
(d) A mixture of hydrogen, deuterium, and tritium was allowed to diffuse through a long tube with a
porous plug at the end of the tube.
[3]
1
(i)
(ii)
(iii)
4.
Which of these gases emerged from the tube first?
Which of these gases emerged last?
How did you come to the above conclusions?
The figure below shows the structure of six atoms.
[3]
(a) Identify two pairs of isotopes from these atoms.
(b) Identify two pairs of elements that belong to the same period of the Periodic Table.
(c) Identify the atom which belong to Group IV of the Periodic Table
5.
The letters in the following list represents some elements. They are not actual symbols of the
elements.
2
80
36
X,
35
17
Y,
17
8
Z,
86
36
Q,
80
34
R
(a) From the list, select a pair of elements with similar chemical properties.
[1]
(b) Why do you think they have similar properties?
[1]
6.
Strontium is used in fireworks to produce crimson flames. Naturally occurring strontium has
three isotopes :
86
87
88
38 Sr (10%); 38 Sr (7%); 38 Sr (83%)
What is the relative atomic mass of naturally occurring strontium?
[3]
*7. Sketch the graph of the number of valence electrons for the atoms of the first 12 elements of the
Periodic Table against the proton (atomic) number of the element.
[3]
8. The element gallium is Group III of the Periodic Table and exists as two isotopes :
3
69
31
Ga and 73 11 Ga
(a) Complete the following table.
[2]
69
71
Ga
Ga
Number of protons
Number of neutrons
Number of electrons
(b) Write down the formula for an ion of gallium.
[1]
(c) Write down the formula for (i) gallium chloride, (ii) gallium carbonate.
[2]
(d) A sample of gallium contains 60.0% of atoms of
relative atomic mass of this sample of gallium.
69
Ga and 40.0% of atoms of
71
Ga. Calculate the
[2]
9. Boron is used to make control rods for nuclear reactors. Naturally occurring boron contains atoms
10
11
represented by the symbols 5 B and 5 B.
(a) Draw the electronic configuration of a boron atom.
[1]
(b) Suggest why the relative atomic mass of naturally occurring boron is not a whole number.
[1]
*10. The following diagram was obtained from an analysis of naturally occurring chlorine isotopes.
4
(a) Using the diagram, calculate the relative atomic mass of a sample of naturally occurring chlorine.
[1]
(b) What is the difference between Cl-37 and Cl-35?
[1]
(c) Explain and compare briefly the physical and chemical properties of isotopes.
[2]
5