Bonding in Discrete Simple Molecules

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Covalent Bonding

Last updated 6:14 AM on 8/30/26
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56 Terms

1
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Define a discrete (simple) molecule.
An electrically neutral group of two or more atoms held together by covalent bonds.
2
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What type of bonding holds atoms together in discrete molecules?
Covalent bonding.
3
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What does a dot-and-cross diagram show?
The outer-shell electrons involved in bonding and any non-bonding electrons.
4
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Why are dots and crosses used in a dot-and-cross diagram?
To show which atom each electron originally came from.
5
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What does one shared pair of electrons represent?
A single covalent bond.
6
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What does a double covalent bond contain?
Two shared pairs of electrons.
7
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What does a triple covalent bond contain?
Three shared pairs of electrons.
8
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What are non-bonding electrons?
Outer-shell electrons that are not involved in covalent bonds.
9
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What is another name for a pair of non-bonding electrons?
A lone pair.
10
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When drawing dot-and-cross diagrams, which electrons usually need to be shown?
Only the outer-shell electrons.
11
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What must be shown around atoms such as chlorine in a dot-and-cross diagram?
All non-bonding outer-shell electrons as well as the bonding electrons.
12
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13
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How many covalent bonds does hydrogen normally form?
1.
14
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How many covalent bonds does carbon normally form?
4.
15
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How many covalent bonds does nitrogen normally form?
3.
16
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How many covalent bonds does oxygen normally form?
2.
17
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How many covalent bonds does a halogen such as chlorine normally form?
1.
18
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How many lone pairs are present on oxygen in H₂O?
2.
19
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How many lone pairs are present on nitrogen in NH₃?
1.
20
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How many lone pairs are present on carbon in CH₄?
0.
21
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How many single covalent bonds are present in water, H₂O?
2.
22
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How many single covalent bonds are present in ammonia, NH₃?
3.
23
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How many single covalent bonds are present in methane, CH₄?
4.
24
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25
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What is the octet rule?
Atoms generally form bonds so that they have eight electrons in their outer shell.
26
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What is the main exception to the octet rule for hydrogen?
Hydrogen becomes stable with 2 electrons in its outer shell.
27
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Do all molecules obey the octet rule?
No.
28
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Which Period 3 elements can form molecules with more than 8 outer-shell electrons?
Elements such as phosphorus and sulfur.
29
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How many electrons surround beryllium in BeCl₂?
4.
30
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How many electrons surround boron in BCl₃?
6.
31
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How many electrons can surround phosphorus in PCl₅?
10.
32
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How many electrons can surround sulfur in SF₆?
12.
33
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Why are BeCl₂ and BCl₃ exceptions to the octet rule?
The central atom has fewer than 8 electrons in its outer shell.
34
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Why are PCl₅ and SF₆ exceptions to the octet rule?
The central atom has more than 8 electrons in its outer shell.
35
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36
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Define a displayed formula.
A formula that shows each atom and the bonds between the atoms.
37
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What does one line in a displayed formula represent?
One shared pair of electrons, or one covalent bond.
38
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How is a single bond represented in a displayed formula?
By one line between two atoms.
39
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How is a double bond represented in a displayed formula?
By two lines between two atoms.
40
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How is a triple bond represented in a displayed formula?
By three lines between two atoms.
41
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42
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What is the displayed formula of water?
H–O–H.
43
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What bonds are present in oxygen, O₂?
One double covalent bond, O=O.
44
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What bonds are present in nitrogen, N₂?
One triple covalent bond, N≡N.
45
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What bonds are present in carbon dioxide, CO₂?
Two double covalent bonds, O=C=O.
46
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How many shared pairs of electrons are in an O=O double bond?
2 shared pairs.
47
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How many shared pairs of electrons are in an N≡N triple bond?
3 shared pairs.
48
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How many bonding electrons are present in a single covalent bond?
2.
49
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How many bonding electrons are present in a double covalent bond?
4.
50
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How many bonding electrons are present in a triple covalent bond?
6.
51
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52
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Why do atoms form covalent bonds?
Sharing electrons allows the atoms to achieve a more stable outer-shell electron arrangement.
53
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What is the key difference between a molecular substance and a giant covalent structure?
A molecular substance contains separate discrete molecules, whereas a giant covalent structure has a continuous network of covalently bonded atoms.
54
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Are ionic crystals made from discrete molecules?
No. They consist of a giant lattice of ions.
55
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Are giant covalent structures made from discrete molecules?
No. Their covalent bonds extend throughout a giant structure.
56
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Are solid metals made from discrete molecules?
No. They consist of a giant metallic lattice.