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COPY RGS 4th Form Chemistry > Covalent Bonding > Flashcards

Covalent Bonding Flashcards

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1
Q

Why do giant covalent compounds have high melting points?

A
  • many strong covalent bonds
  • in giant lattice structure
  • require a lot of energy to overcome
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2
Q

What state of matter is chlorine, bromine and iodine at room temperature?

A

Chlorine- gas

Bromine- liquid

Iodine-solid

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3
Q

How do you draw the structure of graphite?

A
  • Draw a minimum of three hexagons in each layer
  • Off set the layers and add dotted vertical lines between layers to represent the weak force between layers
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4
Q

What sort of bond is between the carbon and oxygen in carbon dioxide?

A

Double covalent bond

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5
Q

If chlorine water is added to sodium iodide solution, the solution turns from colourless to brown.

Why does this happen?

A

Chlorine water (colourless) is more reactive than iodide

Cl2+ 2NaI –> 2NaCl + I2

colourless brown

Chlorine displaces the iodide ion to form iodine

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6
Q

Describe the forces on any outer shell electrons

A

Force of attraction between outer electrons (-) and (+) positive nucleus

Force of repulsion between outer electrons (-) and electrons (-) in middle shells (called electron shielding)

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7
Q

What is the dot cross diagram for chlorine?

A
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8
Q

Describe the appearance of the element chlorine

A

pale green gas at room temperature

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9
Q

What are the names of the two types of covalently bonded substances?

A

Simple covalent e.g. water

Giant covalent e.g. diamond

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10
Q

Below are the many possible structure of the element sulfur.

What are these structures called, which are different structural forms of the same element?

A

allotropes

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11
Q

How do you draw the structure of diamond?

A
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12
Q

What is the dot cross diagram for oxygen?

A
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13
Q

Iodine is a larger atom than bromine.

This means the outer shell is further from nucleus and there is a weaker force of attraction on electrons

This also means there is more electron shielding, more repulsion on the outer shell electrons

What affect does this have on iodine’s reactivity compared to bromine?

A

Iodine is less reactive than bromine.

Remember group 7 wants to gain or share 1 electron and i_odine has less of a pull from the nucleus_ and more repulsion from electrons in the middles shells.

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14
Q

Describe the appearance of chlorine, bromine and iodine

A

Chlorine- pale green gas

Bromine- red liquid

Iodine- grey solid

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15
Q

What would you observe if you add colourless chlorine water to potassium iodide

KI + Cl2

A

It would turn from colourless to brown

chlorine is more reactive than iodine

chlorine will displace iodide ion

2KI + Cl2 –> KCl + I2

colourless brown

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16
Q

Graphite is made of layers which have weak intermolecular forces between them

The layers can easily slide over one another

Does this make graphite hard or soft?

A

soft

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17
Q

What would you observe if you add orange bromine water to potassium iodide

KI + Br2

A

It would turn from orange to brown

bromine is more reactive than iodine

bromine will displace iodide ion

2KI + Br2 –> 2KBr + I2

orange brown

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18
Q

Diamond is an allotrope of carbon.

Carbon has 4 bonds and forms a tight tetrahedral structure with no layers.

It is entirely made of strong covalent bonds and has no weak intermolecular forces

Will diamond be hard or soft?

A

hard

contains no layers which easily slide over one another.

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19
Q

State two uses of diamond and two uses of graphite

A

diamond- cutting tools, jewellery

graphite- lubricant and electrodes for electrolysis

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20
Q

Describe the difference in solubility of both ionic and covalently bonded substances in water

A

-Ionic compounds have generally high solubility

(polar solvents like water can easily pull oppositely charged ions from the structure- dissolving it)

-Covalent compounds have generally low solubility

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21
Q

What is a allotrope? Give two examples

A

Same element but different structure - or are chemically bonded in a different way

e.g.

diamond and graphite are allotropes

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22
Q

What type of atoms covalently bond together?

metal & metal

non-metal & metal

non-metal and non-metal

A

non-metal and non-metal atoms covalently bond

they share electrons.

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23
Q

What is the displayed formula for water?

A
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24
Q

Which sort of bond will form between sulfur and oxygen?

A

Both non-metals, so covalent bond

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25
Q

Draw the dot cross diagram for ammonia

A
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26
Q

Covalent bonds form between which types of atoms?

Ionic bonds form between which types of atoms?

A

Covalent bonding happens between non-metals- they share electrons

Ionic bonding happens between metals and non-metals- electrons are transferred from the metal to the non-metal

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27
Q

Give three examples of simple covalent compounds

A
  1. water H2O
  2. methane CH4
  3. ammonia NH3
  4. chlorine Cl2
  5. Carbon dioxide CO2
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28
Q

Chlorine is a green gas

Bromine is a red liquid

Iodine is a grey solid

What colours are these halogens when in solution such as in displacement reactions?

A

Chlorine solution is colourless

Bromine solution is orange

Iodine solution is brown

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29
Q

Hydrogen chloride is a covalently bonded substance. What happens when hydrogen chloride is added to methylbenzene?

A
  • In methylbenzene (which is a non-polar solvent) hydrogen chloride does not dissociate, it is not pulled apart.
  • There are no H+ ions present therefore blue litmus paper stay blue.
  • It is not acidic
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30
Q

Fluorine is a smaller atom than chlorine.

This means the outer shell is closer to nucleus and there is a greater force of attraction on electrons

This also means there is l_ess electron shielding_, less repulsion on the outer shell electrons

What affect does this have on fluorine’s reactivity?

A

Fluorine is more reactive than chlorine.

Remember group 7 wants to gain or share 1 electron!

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31
Q

What would you observe if you add colourless chlorine water to sodium chloride?

NaCl + Cl2

A

Nothing

Solution would stay colourless

chlorine will not displace chloride ion

chlorine will not displace itself

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32
Q

Describe the reactivity in Group 7- The halogens

A

Reactivity increases up group 7

Fluorine is the most reactive halogen

  • lowest number of shells, outer shell closer to positive nucleus
  • larger attractive forces between nucleus and outer electrons
  • less electron shielding - less repulsion from electrons
  • greater pull on electrons, less energy required to react, more reactive
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33
Q

Is the substance below simple covalent or giant covalent?

A

Simple covalent

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34
Q

What is the dot cross diagram for ethene?

A

Notice the double bond between the two carbon atoms!

35
Q

Describe the appearance of the element chlorine

A

pale green gas at room temperature

36
Q

Why are simple molecular substances usually gaseous at room temperature?

A

They have low melting points

weak intermolecular forces

little energy is needed to overcome them

37
Q

Use the change in appearance of the halogens below to deduce the appearance of astatine (Below iodine in Group 7)

Chlorine- pale green gas

Bromine- red liquid

Iodine- grey/purple solid

A

Black solid

38
Q

What sort of bond is between the nitrogen atoms in nitrogen?

A

Triple covalent bond

39
Q

What giant covalent substance is shown in the image below?

A

diamond

40
Q

What would you observe if you add colourless chlorine water to sodium bromide?

KBr + Cl2

A

It would turn orange

chlorine will displace bromide ion

chlorine is more reactive than bromine

2KBr + Cl2 –> 2KCl + Br2

41
Q

What is the dot cross diagram for nitrogen?

A

Notice the triple bond between the nitrogen!

42
Q

Hydrogen chloride is a covalently bonded substance. What happens when hydrogen chloride is added to water?

A
  • In water (which is a polar solvent) hydrogen chloride dissociates (or is pulled apart) into an H+ ion and Cl- ion.
  • There are H+ ions present therefore blue litmus paper would turn red.
  • This is forms hydrochloric acid.
43
Q

What sort of bond is between oxygen atoms in oxygen?

A

Double covalent bond

44
Q

Why is graphite soft?

A
  • It has weak intermolecular forces between its layers
  • layers can easily slide over each other
  • it does not hold its structure when deformed
45
Q

What would you observe if you add colourless chlorine water to sodium chloride?

NaCl + Cl2

A

Nothing

Solution would stay colourless

chlorine will not displace chloride ion

chlorine will not displace itself

46
Q

What would you observe if you add colourless chlorine water to potassium iodide

KI + Cl2

A

It would turn from colourless to brown

chlorine will displace iodide ion

chlorine is more reactive than iodine

2KI + Cl2 –> 2KCl + I2

47
Q

What type of bond is an electrostatic force of attraction between a shared pair of electrons and the positively charged nucleus of an atom.

A

Covalent bond

48
Q

Describe what happens to the boiling point as you go down Group 7 (The Halogens)

A

Boiling point increases down the group

49
Q

What is a covalent bond?

A

The electrostatic attraction between a shared pair of electrons and the nucleus of an atom.

50
Q

What are the similarities and differences between a covalent bond and an ionic bond?

A

Same- both electrostatic attraction

Different-

Covalent bond- non-metals & non-metal

Ionic bond - metal & non-metal

Different-

Covalent bond- between a shared pair of electrons and nucleus of an atom

Ionic bond- between oppositely charged ions

51
Q

What would you observe if you add brown iodine water to sodium chloride?

NaCl + I2

A

Nothing

Solution would stay brown

Iodine will not displace chloride ion

Iodine is less reactive than chlorine

52
Q

What is the dot cross diagram for hydrogen chloride?

A
53
Q

Name all the diatomic molecules- remember that they are covalently bonded

A

Hydrogen

Nitrogen

Fluorine

Oxygen

Iodine

Chlorine

Bromine

A goof mneumonic is ‘Have No Fear Of Ice Cold Beer’

54
Q

Why do simple covalent compounds have low melting points?

A
  • weak intermolecular forces
  • require little energy to overcome

- low melting point

55
Q

Br2 + CuI2 –> CuBr2 + I2

In the halogen displacement bromine is more reactive than iodine and displaces it, what is oxidised and what is reduced?

A

Br2 + 2e- –> 2Br-

2I- –> I2 + 2e-

OIL RIG

Bromine is reduced- gained electron

Iodide ion is oxidised- loses electron

56
Q

Which sort of bond will form between magnesium and oxygen?

A

One metal and other non-metal. Ionic bond would form.

57
Q

What would you observe if you add colourless chlorine water to sodium bromide?

KBr + Cl2

A

It would turn from colourless to orange

chlorine will displace bromide ion

chlorine is more reactive than bromine

2KBr + Cl2 –> 2KCl + Br2

58
Q

Explain why covalent compounds do not conduct electricity

A
  • There are no mobile ions or electrons
  • No charged particles to carry charge
59
Q

What is similar between a metallic structure, ionic structure and giant covalent structure?

A
  • They all have many strong bonds in a giant structure.
  • They all require a lot of energy to overcome
  • They all have high melting points
60
Q

What is the dot cross diagram for carbon dioxide?

A
61
Q

Why do carbon & carbon share electrons when bonded but sodium & chlorine transfer electrons when bonded?

A
  • Two carbon atoms have equal ‘pull’ or ‘affinity for electrons. Therefore they share electrons.

whereas,

  • Chlorine has a large‘pull’ or affinity for electrons and sodium does not. Therefore sodium transfers one electron to chlorine.
62
Q

What is the dot cross diagram for water?

A
63
Q

Is the substance below simple covalent or giant covalent?

A

Giant covalent

64
Q

Compare and contrast the state of ionic and simple covalent compounds at room temperature

A
  • Ionic compounds are all solid
  • Simple covalent compounds can be gaseous, liquid or solid at room temperature
65
Q

Describe the appearance of the element iodine

A

grey/purple solid at room temperature

66
Q

How are metallic bonds different from/similar to covalent bonds?

A

Same: both are an electrostatic attraction

Different:

Metallic- attraction is between positive metal ions and a sea of delocalised electrons

Covalent is between a nucleus and a shared pair of electrons.

67
Q

What is the dot cross diagram for hydrogen?

A
68
Q

Which sort of bond would form between copper and copper?

A

Both metals - metallic bond.

69
Q

What is the dot cross diagram for methane?

A
70
Q

Why does graphite (a non-metal) conduct electricity?

A
  • Graphite is made of layers of carbon atoms with three bonds.
  • Carbon is in group 4 and has four outer electrons.
  • This one electron is free to move (delocalised) within the layers of carbon
  • and can carry charge.
71
Q

What are the similarities and differences between a covalent bond and metallic bond?

A

Same: They are both an electrostatic attraction

Difference:

Covalent bond- is between a shared pair of electrons and the nucleus of an atom

Metallic bond- is between a metal ion and a sea of delocalised electrons

Difference:

Covalent bond- between non-metals only

Metallic - between metals only

72
Q

Compare and contrast the properties of graphite and diamond

appearance

harness

thermal conductivity

electrical conductivity

use

A
73
Q

What is the dot cross diagram from ammonia?

A
74
Q

How many outer electrons do the halogen group have?

A

seven outer electrons

All halogens atoms form diatomic simple molecular molecules

F2

Cl2

I2

75
Q

What would you observe if you add orange bromine water to sodium chloride?

NaCl + Br2

A

Nothing

Solution would stay orange

Bromine will not displace chloride ion

Bromine is less reactive than chlorine

76
Q

Explain why graphite makes a good lubricant

A
  • Graphite has weak forces between the layers
  • layers can slide over one another easily
77
Q

Give three examples of giant covalent compounds

A
  1. graphite
  2. diamond
  3. silicon dioxide
78
Q

Describe the appearance of the element bromine

A

red liquid at room temperature

79
Q

Describe the appearance of the element bromine

A

red liquid at room temperature

80
Q

Fluorine is a smaller atom than chlorine.

This means the outer shell is closer to nucleus and there is a greater force of attraction on electrons

This also means there is l_ess electron shielding_, less repulsion on the outer shell electrons

What affect does this have on fluorine’s reactivity?

A

Fluorine is more reactive than chlorine.

Remember group 7 wants to gain or share 1 electron!

81
Q

How are the covalent bonds between carbon in diamond different from the covalent bonds between carbon in graphite?

A

Diamond- all four outer shell electrons are used

Graphite- only 3 outer shell electrons are used- fourth electron exists between the layers and is delocalised

82
Q

Why does tetrachloromethane have a higher boiling point than trichloromethane?

A

Tetrachloromethane has a higher formula mass, therefore has a higher boiling point

    • larger forces between the molecules*
  • -more energy needed to overcome them*
83
Q

Is fullerene giant covalent or simple covalent?

A

Simple covalent

It is molecular and has a definite size

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