Name: …………………… (
Chem!stry
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Assignment One on Chemical Bonding – Answers
 Ions:
1.
2.
3.
Atoms of metallic elements become ions by…
A
Gaining electrons
B
Sharing electrons
C
Losing electrons
D
Gaining electrons
Element Z has six valence electrons. Its ion is represented by…
A
Z+
B
Z–
C
Z2+
D
Z2–
The diagram below shows the atomic structure of two particles, X and Y.
Particle X
Particle Y
Complete the table below for both particles.
Particle X
Particle Y
Name of Element
Beryllium (symbol Be)
Nitrogen (symbol N)
Nuclide Notation
11
4Be
14
7N
Electronic Configuration
2,2
2,5
Formula of Ion Formed
Be2+
N3–
1
)
4.
Using the information given in the table, answer the following questions.
a)
Element
Atomic Number
Mass Number
Electronic
Configuration
A
4
9
2,2
B
10
20
2,8
C
17
35.5
2,8,7
D
12
24
2,8,2
E
19
39
2,8,8,1
State two elements that are able to form ions with the same electronic configuration as
argon.
Argon has the electronic configuration 2,8,8. Element C can obtain this electronic
configuration by gaining one electron. Element E can obtain this electronic configuration
by losing one electron.
b) Which element(s) form positive ion(s)? For each element that forms a positive ion, write
down the formula of the ion formed (use the symbols given in the question).
A and D will lose two electrons to obtain the electronic configuration of a noble gas. E will
lose one electron to obtain the electronic configuration of a noble gas. A2+, D2+ and E+.
c)
Which element(s) form negative ion(s)? For each element that forms a negative ion, write
down the formula of the ion formed (use the symbols given in the question).
C will gain one electron to obtain the electronic configuration of a noble gas. C–.
5.
The atomic number of aluminium is 13. Write the electronic configuration of the aluminium ion.
The electronic configuration of an aluminium atom is 2,8,3. An atom of aluminium loses its
three valence electrons to obtain a noble gas electronic configuration. The electronic
configuration of an aluminium ion, Al3+, is therefore 2,8.
6.
Give the nuclide notation of a known element / ion that contains 18 electrons, 16 protons and
16 neutrons.
Element with an atomic number of 16 is sulfur. Mass number = 16 protons + 16 neutrons = 32
The particle contains two more negatively charged electrons compared to the number of
positively charged protons and therefore carries a charge of 2–. Nuclide notation is 3216S2–.
7.
Calcium forms the ion Ca2+. How many protons and electrons does a single Ca2+ ion contain?
Number of protons:
Calcium has an atomic number of 20. Protons = 20.
Number of electrons: A charge of 2+ means two more protons than electrons. Electrons = 18.
2
8.
Draw the stated diagrams for the following ions.
Dot-and-cross diagram showing the full
electronic configuration – all electrons
and shells:
b) A magnesium ion, Mg2+
Mg2+
c) A potassium ion, K+
a) A chloride ion, Cl–
Dot-and-cross diagram showing the
valence electrons only:
K1+
 Ionic Bonding:
9.
a)
Draw a dot-and-cross diagram, showing the valence electrons only, to show the bonding
in magnesium fluoride.
b) The chemical formula of magnesium fluoride is: MgF2
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10. The table below gives the electronic configurations of five elements.
Element
Electronic Configuration
A
2,3
B
2,8,7
C
2,8,1
D
2,8,8
E
2,6
Use the information given in the table to answer the following questions.
a)
i)
Element B and C react to form a compound. Draw a dot-and-cross diagram, showing
the valence electrons only, to show the bonding between elements B and C.
ii)
The formula of the compound formed between elements B and C is: CB
 Note: When writing formulae, the symbol of the metal is written first.
b) i)
Element C and E react to form a compound. Draw a dot-and-cross diagram, showing
the valence electrons only, to show the bonding between elements C and E.
ii)
The formula of the compound formed between elements C and E is: C2E
 Note: When writing formulae, the symbol of the metal is written first.
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11. The table below gives the locations of six different chemical elements in the Periodic Table.
Element
Group Number
Period Number
P
2 (II)
2
Q
1 (I)
4
R
13 (III)
3
S
17 (VII)
3
T
16 (VI)
2
U
17 (VII)
4
Use the information given in the table to answer the following questions.
Write the chemical formula for the compound formed by elements:
a)
P and S: P, Group 2, valency = 2. S, Group 17, valency = 1. Formula = PS2.
b) Q and T: Q, Group 1, valency = 1. T, Group 16, valency = 2. Formula = Q2T.
c)
R and U: R, Group 13, valency = 3. U, Group 17, valency = 1. Formula = RU3.
12. W, X, Y and Z are four consecutive elements with atomic numbers n, n + 1, n + 2 and n + 3
respectively. Y is a chemically inert gas.
Note: W is in Group 16, X is in Group 17, Y (a noble gas) is in Group 18 and Z is in Group 1.
a)
Element W and element Z react together to form a solid compound T.
i)
State the type of bonding found in compound T.
Non-metal W and metal Z will react to form an ionic compound / ionic bonding.
ii)
Give the formula of compound T.
Z2W. Metal from Group 1 with non-metal from Group 16. Symbol of metal is written first.
b) Element X forms a compound with element Z.
i)
Give the formula of the compound formed between element X and element Z.
ZX. Metal from Group 1 with non-metal from Group 17. Symbol of metal is written first.
ii)
Draw a dot-and-cross diagram, showing the valence electrons only, to show the
bonding between element X and element Z.
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13. What is the chemical formula of a compound formed between a Group 2 (II) element X and a
Group 16 (VI) element Y?
X, Group 2, valency = 2. Y, Group 16, valency = 2. Formula = XY.
14. a)
Draw lines to match the names of the polyatomic ions with their formulae.
b) Element A is silvery grey in colour and forms a compound with hydroxide ions (OH–)
which has the formula AOH. Which Group of the Periodic Table does element A belong
to?
Element A is silvery grey and is therefore a metal. An atom of element A loses a single
electron to form the ion A+, with a single positive charge, equal and opposite to OH–. A is
a Group 1 metal because Group 1 metals all form cations with a single positive charge.
15. Which Group of the Periodic Table does element D belong to if it forms a compound with
calcium which has the formula CaD2?
Assume CaD2 is ionic, calcium is a metal and D is a non-metal. The formula of the calcium ion
is Ca2+. There are two ions of D, each ion carries a single negative charge, D–. An atom of
element D gains one electron (one negative charge) to obtain the electronic configuration of a
noble gas. Element D has seven valence electrons and is in Group 17 of the Periodic Table.
Covalent Bonding
16. The electronic configurations of elements U, V, W, X and Y are shown below:
U: 2,8,1 (metal)
V: 2,8,6 (non-metal)
W: 1 (non-metal)
X: 2,7 (non-metal)
Y: 2,4 (non-metal)
Complete the table below to indicate the type of bonding (ionic or covalent) and the formula of
the compound that is formed when the following pairs of element react and bond together.
Elements
U and W
V and Y
W and Y
U and X
Type of Bond
Ionic
Covalent
Covalent
Ionic
Formula of Compound
UW
YV2
YW4
UX
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17. Hydrogen chloride is a covalent compound while sodium chloride is an ionic compound.
a)
Explain, in terms of electrons, how a covalent compound differs from an ionic compound.
Covalent: Valence shells of the non-metallic atoms overlap. Atoms of non-metallic
elements share electrons in order to obtain the electronic configurations of noble gases. A
shared pair of electrons is a covalent bond.
Ionic: There is electron transfer from atoms of the metallic element to atoms of the
non-metallic element. The metallic element forms positively charged ions (cations) with
noble gas electronic configuration. The non-metallic element forms negatively charged
ions (anions) with noble gas electronic configuration.
b) Explain how a covalent compound differs from an ionic compound in terms of the type of
elements that typically form the compounds.
Covalent bonding typically takes place between atoms of non-metallic elements only.
The atoms may be of the same non-metallic element or different non-metallic elements.
Ionic bonding typically takes place when a metallic element bonds with a non-metallic
element.
18. Draw dot-and-cross diagrams, showing the valence electrons only, to show the bonding
present in the compounds formed when the following pairs of elements combine together.
a) hydrogen and chlorine
b) hydrogen and oxygen
c) carbon and hydrogen
d) carbon and oxygen
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