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Chemistry > Chapter 4: Covalent Bonding > Flashcards

Chapter 4: Covalent Bonding Flashcards

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1
Q

Where are noble gases located in the Periodic Table?

A

Group 18

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2
Q

What are the properties of noble gases?

A
  1. Low melting and boiling points
  2. Insoluble in water
  3. Colourless gases at room temperature
  4. Odourless
  5. Unreactive
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2
Q

What can neon be used for?

A

Make lights or advertisement signs

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2
Q

What can helium be used for?

A

Fill weather balloons, advertisement balloons or airships.

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3
Q

What can argon be used for?

A

To fill tungsten light bulbs and to provide an inert atmosphere for certain processes such as welding steel.

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4
Q

What do noble gases having a fully filled valence shell mean?

A

They do not gain, lose or share electrons with other elements. Thus, they do not react with other elements to form compounds and are said to be unreactive. They thus exist as monatomic gases.

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4
Q

Why are noble gases inert?

A

They have a fully-filled valence shell of eight electrons, except helium with 2 valence electrons

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4
Q

Why is argon used to fill tungsten light bulbs?

A

It provides an inert atmosphere to help protect the tungsten from oxidation in air.

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5
Q

What can xenon be used for?

A

In vehicle headlamps.

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6
Q

What are the 2 types of ions, what charges do they have and what type of elements are they created from?

A

Cations: Positively charged ions (metals)
Anions: Negatively charged ions (non-metals)

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7
Q

Define ‘ion’

A

They are charged particles that are formed when atoms gain or lose electrons.

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7
Q

What are polyatomic ions?

A

Ions of 2 or more covalently bonded atoms with an overall charge

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8
Q

Why do atoms need to gain or lose electrons?

A

To achieve a fully-filled valence shell in order to have the same electronic structure as a noble gas.

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9
Q

What are monatomic ions?

A

Single ions that have a postive or negative charge

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10
Q

Why do elements choose to lose an electron, rather than gain 7 electrons?

A
  1. If you gain 7 electrons, the element will then have an overall charge of -7. The large number of negative charges in the electrons will repel each other.
  2. It is easier to lose an electron rather than gain7 as less energy is required to gain one electron than to gain 7 electrons.
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11
Q

What is an ionic bond?

A

The strong electrostatic forces of attraction between postive and negative ions

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11
Q

What happens after covalent bonding takes place?

A

Each atom attains a fully-filled valence shell, and a molecule is formed.

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11
Q

When are ionic compounds formed?

A

When metals atoms transfer over their electrons to non-metal atoms.

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11
Q

What are the physical properties of ionic compounds?

A
  1. High melting and boiling points
  2. Conducts electricity in molten or aqueous state, but not in the solid state.
  3. Most ionic compounds are soluble in water but insoluble in organic compounds.
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11
Q

Explain the property: High melting and boiling points (Ionic Compounds)

A
  1. Ionic compounds have a giant ionic lattice structure. The electrostatic forces of attraction between the postive and negative ions are very strong. A large amount of heat energy is required to overcome these strong forces of attraction.
  2. Used as refractory materials (heat-resistant).
    Magnesium oxide used to line the interior of blast furnaces, aluminium oxide used to make crucibles and spark plugs for motor cars.
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12
Q

Explain the property: ‘Conduct electricity in molten or aqueous state, but not in solid state’

A
  1. In molten and aqueous state, the ions can move freely to conduct electricity through the susbtance.
  2. In solid state, the ions are held in fixed positions by the strong electrostatic forces of attraction, thus they are unable to move freely to conduct electricity.
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12
Q

Explain the property: ‘Most ionic compounds are soluble in water, but insoluble in organic compounds.’

A

Water molecules are attracted to ions, weakening the electrostatic forces of attraction between the ions. As a result, ions are pulled from the lattice structure and the compound dissolves to form an aqueous solution. (Process: Dissociation)

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12
Q

What are the factors affecting strength of ionic bond?

A
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12
Q

What is a covalent bond?

A

A bond formed when there is a sharing of electrons between 2 non-metal atoms.

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12
What can covalent bonds be formed between?
1. Atoms of the same element (molecule of elements) 2. Atoms of different elements (molecule of compounds)
12
What are the 3 types of covalent bonds and what do they involve?
1. Single covalent bond (share 2 electrons) 2. Double covalent bond (share 4 electrons) 3. Triple covalent bond (share 6 electrons)
13
Define 'molecule'
A group of two or more atoms joined together by covalent bonds
14
What can covalent bonds be formed between?
1. Atoms of the same element (molecule of elements) 2. Atoms of different elements (molecule of compounds)
14
What kind of structure do most covalent substances have?
Simple molecular structure.
15
What are the properties of simple molecular susbtances?
1. Low melting point and boiling point 2. Non-conductor of electricity 3. Usually insoluble in water, usually soluble in organic solvents.
15
Explain these properties of simple molecular substances. (Low melting point and boiling point)
Structure: Covalent substances have simple molecular structure. Attraction: Covalent compounds are held together by weak intermolecular forces of attraction. Energy: Only a little amount of heat energy is required to overcome these forces of attraction.
16
Explain these properties of simple molecular substances. (Non-conductor of electricity)
Covalent substances are uncharged
16
What are the special covalent substances that do not have a simple molecular structure?
1. Diamond 2. Silicon dioxide 3. Graphite
17
What is the structure and bonding of diamond?
1. Giant molecular tetrahedral structure. 2. 1 carbon atom is covalently bonded to 4 other carbon atoms.
18
What are the properties of diamonds?
1. High melting and boiling point 2. Non-conductor of electricity. 3. Hard
19
What are the uses of diamonds?
Tips of grinding, cutting and polishing tools.
20
What is the structure and bonding of silicon dioxide?
1. Giant molecular tetrahedral structure 2. 1 silicon atom form 4 covalent bonds with 4 oxygen atoms while each oxygen atom is bonded to 2 silicon atoms.
20
What are the properties of silicon dioxide?
1. High melting and boiling point 2. Non-conductor of electricity
21
What are the uses for silicon dioxide?
It is a main component of concrete and glass production.
21
What is the structure and bonding of graphite?
1. Giant molecular layered structure. 2. 1 carbon atom is covalently bonded to 3 other carbon atoms, causing it to have continuous hexagonal rings.
21
What can graphite be used for?
1. As a dry lubricant 2. As inert electrodes
21
What are the properties of graphite?
1. High melting and boiling point 2. Good conductor of electricity 3. Soft and slippery.
21
What are the explanations for the physical properties of covalent substances that have giant molecular structure? (HBMP)
1. Atoms in the giant molecular structure are held together by an extensive network of strong covalent bonds between atoms 2. A large amount of energy is required to overcome these bonds.
22
Why is graphite a good conductor of electricity?
As 1 carbon atom is covalently bonded to 3 other carbon atoms, this leaves one valence electron per carbon atom that is not invovled in bonding, it moves freely along graphite layers and conducts electricity parallel to the hexagonal layers.
22
Why is graphite soft?
The layers of hexagonal rings that graphite has are held together by weak intermolecular forces of attraction. Thus, these layers can slide over each other when a force is applied.
23
What are the explanations for the physical properties of covalent substances that have giant molecular structure? (Insoluble in water and organic solvents)
1. All atoms are held together by strong covalent bonds. 2. Any forces of attraction between the giant molecular structure and solvent molecules are not strong enough to break the strong covalent bonds.
23
What are the physical properties of covalent substances? (Giant molecular structures)
1. High melting and boiling point 2. Non-conductor of eelctricity (Except graphite) 3. Usually insoluble in water and organic solvents.
24
What are the explanations for the physical properties of covalent substances that have giant molecular structure? (Non-conductor of electricity)
1. All outer electrons are used to form covalent bonds. 2. There are no free elctrons that move through the structure to conduct electricity.
25
What can we compare between ionic and covalent bonding?
1. Ionic bonds are formed between metals and non-metals, while covalent bonds are formed between non-metals. 2. Ionic bonds involve the transfer of electrons, while covalent bonds involve the sharing of electrons. 3. Both ionic bonds and covalent bonds have all atoms involved in the bonding that achieve a fullt-filled valence shell.
26
What is a metallic bond?
The electrostatic force of attraction between positive metal ions and 'a sea of delocalized electrons'
27
What are the properties of metals?
1. High melting and boiling point 2. Good conductors of electricity 3. Usually have high densities 4. Malleable and ductile
27
Explain the properties of metals. (High melting and boiling point)
A large amount of energy is required to overcome the strong electrostatic forces between the cations and the sea of delocalised electrons.
27
What kind of structure does a metal have?
Giant mettalic lattice structure
28
Explain the properties of metals. (Usually have high densities)
Layers of atoms are packed tightly together with little space between them.
28
Explain the properties of metals. (Malleable and ductile)
1. In the solid state, the atoms are orderly arranged. 2. When a force is applied, the layers of atoms can slide over one another easily.
28
Explain the properties of metals. (Good conductors of electricity)
Presence of delocalised electrons to conduct electricity.
28
What is an alloy?
A mixture of metal with one or a few other elements.
29
What are the reasons why we make alloys?
1. To make metals harder and stronger 2. To make metals more resistant to corrosion 3. To improve the appearance of metals. 4. To lower the melting point of metals.
30
What are examples of alloys that are harder and stronger? Tell me about their composition.
1. Brass (Copper, zinc) 2. Steel (Iron, carbon)
30
What is the property of brass?
It is harder and stronger than pure copper.
31
What is the property of steel?
It is harder and stronger than pure iron
32
What can brass be used in?
Make musical instruments and coins
33
What is the property of steel?
Harder and stronger than pure iron.
34
Tell me what an example of an alloy that is more resistant to corrosion. What is its composition?
Stainless steel. Iron, chromium, nickel, carbon
34
What can steel be used in?
Construction of infrastructure and buildings
35
What is the property of stainless steel?
More resistant to corrosion than pure iron.
36
What can stainless steel be used in?
Cutlery and medical instruments
37
What is an example of an alloy where its appearance is improved? What are its components?
Pewter. Tin, antimony and copper
38
What is the property of pewter?
Bright and shiny colour like silver
39
What can pewter be used in?
Decorative ornaments.
39
What is the property of solder?
Lower melting point than pure tin or pure lead.
40
What is an example of an alloy whose melting point is lower? What are its components?
Solder. Tin and lead.
41
Why do alloys become stronger than pure metals?
1. In pure copper, the atoms are of the same size and packed regularly in layers. 2. Hence, it is easy for the layers of atoms to slide over each other when a force is applied. 3. When zinc is mixed with copper, zinc atoms have a different size from copper atoms. 4. This disrupts the regular arrangement of atoms in the pure metal. 5. The atoms of different sizes cannot slide over each other easily when a force is applied, making brass harder and stronger than pure copper.
41
What can solder be used for?
Joining metals together.

Chemistry (4 decks)

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