Chemical Bonding Flashcards

1
Q

What is a compound?

A

A substance that is made up of two or more different elements, chemically combined.

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2
Q

How are atoms held together?

A

By chemical bonds

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3
Q

Describe noble gases

A

They contain 8 electrons in their outer shell and are generally unreactive.

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4
Q

What are the uses of helium?

A
  • Airships because it is not flammable.

- Balloons because it is lighter than air.

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5
Q

What are the uses of argon?

A

Used in lightbulbs to stop imploding.

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6
Q

What is the octet rule?

A

When bonding occurs, atoms tend to reach an electron arrangement with 8 electrons in the outer shell.

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7
Q

What are the limitations of the octet rule?

A
  • Hydrogen
  • Lithium
  • Transition Elements
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8
Q

What is a valency?

A

It is the number of bonds an atom makes when it reacts.

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9
Q

What is a transition metal?

A

It is a metal that forms at least one ion with a particularly filled ‘d’ sublevel.

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10
Q

List three facts about transition metals which could be good to know.

A
  • They have a variable valency.
  • They form coloured compounds
  • They are used mainly as catalysts.
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11
Q

What are the two exceptions of transition metals?

A
  • Zinc (Zn)

- Scandium (Sc)

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12
Q

What is ionic bonding?

A

It is the transfer of electrons.

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13
Q

What is an ion?

A

A charged atom/group of atoms.

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14
Q

What is the charge of a cation?

A

Positive

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15
Q

What is the charge of an anion?

A

Negative

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16
Q

List the chemical equation of how cations formed.

A

Na —> (Na+) + (e-)

Ca —> (Ca2+) + (2e-)

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17
Q

List the chemical equation of how anions formed.

A

Cl- —> (Cl) + (e-)

O2- —> (O) + (2e-)

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18
Q

Define ionic compounds.

A

It is the force of attraction between oppositely charged ions in a compound.

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19
Q

What are the characteristics of ionic substances?

A
  • Strong forces between the ions mean it is very hard to break up due to the lattice structure.
  • Cannot conduct electricity when solid but can when dissolved in water.
  • Most dissolvable in water.
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20
Q

With ionic substances, comment on the:

  • boiling and melting points.
  • the state that it’s in at room temperature.
A

Both boiling and melting points are high and it is solid at room temperature.

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21
Q

Name two everyday examples of ionic substances.

A
  • Table salt (Sodium Chloride) (NaCl)

- Floridation (Sodium Floride) (NaF)

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22
Q

When is a covalent bond formed?

A

When atoms share electrons.

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23
Q

What is an example of a single covalent bond?

A

H2

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24
Q

What is an example of a double covalent bond?

A

O2

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25
Q

What is an example of a triple covalent bond?

A

N2

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26
Q

What are bonding pairs?

A

They have shared electron pairs that form covalent bonds.

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27
Q

What are lone pairs?

A

They are electron pairs that aren’t involved in covalent bonds.

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28
Q

What happens to the orbitals in a covalent bond?

A

The orbitals overlap each other

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29
Q

How are sigma bonds formed?

A

They are formed by the head-on overlap of two orbitals (can be s or p orbitals).

30
Q

How are pi bonds formed?

A

They are formed by the sideways overlap of p-orbitals.

31
Q

Why are sigma bonds stronger than pi bonds?

A

There is more of an overlap between orbitals with sigma bonds than pi bonds.

32
Q

What bonds do a single covalent bond possess?

A

1 sigma

33
Q

What bonds do a double covalent bond possess?

A

1 sigma + 1 pi

34
Q

What bonds do a triple covalent bond possess?

A

1 sigma + 2 pi

35
Q

Briefly outline 3 differences between ionic and covalent bonds.

A

Ionic

  • Transfer of electrons
  • Ions formed
  • Usually solid at room temperature

Covalent

  • Sharing electrons
  • Covalent bond formed
  • Usually liquid or gas at room temperature.
36
Q

How are molecules formed?

A

They are formed when atoms are joined together by covalent bonds.

37
Q

What do you use to figure out the arrangement of atoms in a molecule?

A

You use the Valence Shell Electron Pair Repulsion theory (VSEPR).

38
Q

Talk about the lone pairs around the central atom and how that has an effect on the shape of the molecule.

A

Lone pairs are closer to the nucleus of the atom which means they are closer together (forming a stronger negative). Their collective nuclear charge pushes the bonding pairs further apart, decreasing the bond angle and distorts the shape of the molecule (i.e. H20).

39
Q

Talk about the bonding pairs around the central atom.

A

The electrons in the bonding pairs repel each other and want to be as far apart as possible.

40
Q

For a substance that has 2 bonding pairs:

  • What is the shape?
  • What’s an example?
  • What is the bond angle?
A

Shape - Linear
Example - BeH2
Bond angle - 180*

41
Q

For a substance that has 3 bonding pairs:

  • What is the shape?
  • What’s an example?
  • What is the bond angle?
A

Shape - Trigonal planar
Example - BCl3
Bond angle - 120*

42
Q

For a substance that has 4 bonding pairs:

  • What is the shape?
  • What’s an example?
  • What is the bond angle?
A

Shape - Tetrahedral
Example - Ch4
Bond angle - 109.5*

43
Q

In order of most powerful to least powerful of repulsion, name the 3 types between lone pairs and bonding pairs.

A

Most - lone and lone
Moderate - lone and bonding
Weakest - bonding and bonding

44
Q

In the NH3 molecule:

  • How many bond pairs are present?
  • How many lone pairs are present?
  • What is the bond angle?
  • What is the shape of the molecule?
A

B.P - 3
L.P - 1
B.A - 107*
Shape - Pyramidal

45
Q

In the H20 molecule:

  • How many bond pairs are present?
  • How many lone pairs are present?
  • What is the bond angle?
  • What is the shape of the molecule?
A

B.P - 2
L.P - 2
B.A - 104.5*
Shape - V-shaped

46
Q

What is meant when it is said that an atom is non-polar?

A

It is when atoms in a covalent bond share electrons equally (eg H2, N2, O2).

47
Q

What is meant when it is said that an atom is polar?

A

It is when atoms in a covalent bond don’t share electrons equally (eg HCl, NH2).

48
Q

What is electronegativity?

A

It is the relative attraction an atom has for a shared pair of electrons in a single covalent bond.

49
Q

What happens when the electronegativity increases?

A

The pull also increases.

50
Q

Why is there an increase of electronegativity across the periodic table?

A
  • An increased nuclear charge.

- A decreased atomic radius.

51
Q

Why is there a decrease of electronegativity down the periodic table?

A
  • Screening is in effect.

- Increase in atomic radius.

52
Q

How do you know the difference between the negative and positive dipoles?

A

The atom that has a slightly greater pull on the electrons is the negative dipole and the other atom(s) are the positive dipole(s).

53
Q

Give an example of a molecule with positive and negative dipoles.

A

H20
H - (𝛿)
H - (𝛿)
O- (𝛿2-)

54
Q

What bond types are formed with these values of electronegativity:

  • (0.00 - 0.40)
  • (0.41 - 1.70)
  • (1.71 - +)
A
  • Non-polar covalent
  • Polar covalent
  • Ionic
55
Q

Give two examples of everyday polar substances

A
  • Water

- Ethanol

56
Q

Give two examples of everyday non-polar substances

A
  • Tetrachloroethene

- Acetone

57
Q

Can a molecule that has polar bonds be non-polar overall?

A

Yes, if it one of the following shapes;

  • Linear
  • Planar
  • Tetrahedral
58
Q

If a molecule is a-symmetrical, what shape is it?

A
  • Pyramidal

- V-shaped

59
Q

What is intramolecular bonding?

A

It is bonding within the molecule (eg between hydrogen and oxygen atoms in H20).

60
Q

What is intermolecular bonding?

A

It is bonding between molecules (between H20 molecules).

61
Q

What are the three types of intermolecular bonding?

A
  • Van der Waal
  • Dipole-Dipole
  • Hydrogen
62
Q

What are Van der Waal forces?

A

They are weak forces of attraction between temporary dipoles.

63
Q

Where are temporary dipoles set up?

A

In non-polar molecules.

64
Q

How long do Van der Wall’s last?

A

Not very long and they have low boiling points.

65
Q

Do Van der Wall’s have a high or low boiling point?

A

They have a low boiling point.

66
Q

What are dipole-dipole forces?

A

They are forces of attraction between the negative pole of one molecule and the positive pole of another.

67
Q

What is the dipole-dipole strength in relation to ionic bonds?

A

They are much weaker than ionic bonds.

68
Q

What is hydrogen bonding?

A

Hydrogen bonding occurs in molecules where an atom of hydrogen is bonded to nitrogen, oxygen or fluorine. The hydrogen then carries a positive charge and is attracted to the electronegative atom in another molecule.

69
Q

What boiling points do hydrogen atoms have?

A

They have high boiling points.

70
Q

What three elements are the most electronegative?

A
  • Nitrogen
  • Oxygen
  • Fluorine