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bonding and structure Flashcards

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1
Q

Why do simple molecular structures have low melting and boiling point

A

Small amount of energy is enough to overcome the intermolecular forces

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2
Q

Describe how metals are malleable and ductile

A

Layers of positive ions can easily slide over one another and take up different positions

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3
Q

In which direction of the periodic table does electronegativity increase

A

Top right, towards flourine

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4
Q

What is the strongest type of intermolecular force

A

Hydrogen bonding

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5
Q

What is meant by intermolecular force

A

Attractive forces between neighbouring molecules

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6
Q

Why is ice less dense than water

A
  • In ice, the water molecules are arranged in an open lattice with hydrogen bonds
  • In water, the lattice is collapsed and the molecules are closer together
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7
Q

Does boiling point increase or decrease going down the noble gas group, why?

A
  • Boiling point increases
  • Because the number of electrons increases
  • And the strength of london forces also increases
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8
Q

How many covalent bonds does oxygen form?

A

2

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9
Q

What are the 3 main types of chemical bonds

A
  1. Ionic
  2. Covalent
  3. Metallic
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10
Q

Why do simple molecular structures not conduct electricity

A

They have no free charged particles to move around

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11
Q

Why do giant covalent structures have high melting and boiling points

A

Strong covalent bonds within the molecules need to be broken which requires a lot of energy

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12
Q

Simple molecular structures dissolve in what type of solvent?

A

Non polar solvents

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13
Q

Describe pernament dipole-dipole interactions

A
  • Some molecules with polar bonds have permanent dipoles
  • Leading to forces of attraction between those dipoles and those of neighbouring molecules
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14
Q

In what type of solvents do ionic lattices dissolve?

A

Polar solvents

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15
Q

Define electronegativity

A

The ability of an atom to attract the pair of electrons (the electron density) in a covalent bond

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16
Q

How many covalent bonds does carbon form?

A

4

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17
Q

What is formed when atoms share two pairs of electrons

A

Double bond

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18
Q

Why do giant ionic lattices conduct electricity when liquid, but not when solid?

A
  • In a solid state the ions are in a fixed position and cannot move and carry charge
  • When they are in a liquid state the ions are mobile and can freely carry the charge
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19
Q

How is a polar bond formed

A

Bonding atoms have different electronegativities

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20
Q

What is the most electronegative element

A

Flourine

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21
Q

Define ionic bonding

A

The electrostatic attraction between positive and negative ions

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22
Q

Can simple molecular structures conduct electricity?

A

No they are non-conductors

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23
Q

What does the shape of a molecule depend on?

A
  • Number of electron pairs in the outer shell
  • Number of these electrons which are bonded and lone pairs
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24
Q

Why is H2O polar, whereas CO2 is non polar

A

CO2 is a symmetrical molecule so there is no overall dipole

25
Q

What is avarage bond enthalpy?

A

Measure of average energy needed to break the covalent bond

26
Q

Define metallic bonding

A

Electrostatic attraction between the positive metal ions and the sea of delocalised electrons

27
Q

Describe the bonding in simple molecular structures

A

Atoms within the same molecule are held by strong covalent bonds and different molecules are held by weak intermolecular forces

28
Q

How does graphite conduct electricity

A
  • Delocalised electrons present between the layers are able to move freely carrying the charge
29
Q

Give examples of giant covalent structures

A
  1. Diamond
  2. Graphite
  3. Silicon dioxide
30
Q

What does expansion of the octet mean?

A

When a bonded atom has more than 8 electrons in the outer shell

31
Q

Why does water have a higher melting/boiling point than expected

A
  • Hydrogen bonds are stronger than other intermolecular forces so extra strength is required to overcome the forces
32
Q

List properties of giant covalent structures

A
  1. High melting and boiling point
  2. Non conductors of electricity, except graphite
  3. Insoluble in polar and non-polar solvents
33
Q

Why are ionic compounds soluble in water?

A
  • Water has a polar bond
  • Hydrogen atoms have a 1+ charge and oxygen atoms have a 2- charge
  • These charges are able to attract charged ions
34
Q

What does it mean when the bond is non-polar

A

The electrons in the bond are evenly distributed

35
Q

Describe how metals have high melting and boiling point

A

Many strong metallic bonds in giant metallic structures so large amounts of heat energy are required to overcome forces and break these bonds

36
Q

By how many degrees does each lone pair reduce the bond angle

A

2.5

37
Q

Describe how metals are good conductors of electricity and heat

A

There are free electrons that are available to move and carry charge

38
Q

What conditions are needed for hydrogen bonding to occur

A
  • O-H, N-H, F-H bond, lone pair of electrons on O, F, N
  • O, N, F are highly elecronegative so the H nucleus is exposed
  • Strong force of attraction between H nucleus and lone pair of electrons on O, N, F
39
Q

What is a lone pair?

A

Electrons in the outer shell that are not involved in bonding

40
Q

What is a dative covalent bond

A

A bond where both of the shared electrons are supplied by one atom

41
Q

What is formed when atoms share three pairs of electrons?

A

Triple bond

42
Q

What is it called when atoms are bonded by a single pair of shared electrons?

A

Single bond

43
Q

What are the 2 interactions that can be referred as Van Der Waals’ forces

A
  • Pernament dipole interaction
  • Induced dipole interaction
44
Q

Describe London forces

A
  • London forces are caused by random movements of electrons
  • Leading to instantaneous dipoles
  • Instantenous dipole induces a dipole in nearby molecules
  • Induced dipoles attract one another
45
Q

Are London forces greater in smaller or larger molecules

A

Larger due to more electrons

46
Q

What are the types of intermolecular forces

A
  1. Hydrogen bonds
  2. Pernament dipole-dipole
  3. Induced dipole-dipole (London)
47
Q

Do giant ionic lattices have high or low melting and boiling points? Explain your answer

A
  • They have high melting and boiling points
  • Because a large amount of energy is required to overcome the electrostatic bonds
48
Q

How are oxonium ions formed?

A

When acid is added to water, H3O+

49
Q

Explain induced dipole-dipole interactions

A
  • When a molecule with a pernament dipole is close to another non-polar molecule it causes the non-polar molecule to become slightly polar leading to attraction
50
Q

Define covalent bonding

A

The electrostatic attraction between a shared pair of electrons and the nuclei

51
Q

List the types of structures that covalent molecules form

A
  • Simple molecular lattice
  • Giant covalent lattice
52
Q

Describe the tetrahedral shape

A
  • Angle: 109.5
  • Bond pairs: 4
  • Lone pairs: 0
53
Q

Describe the linear shape

A
  • Angle: 180
  • Bond pairs: 2
  • Lone pairs: 0
54
Q

Describe the trigonal bipyramid shape

A
  • Angle: 90
  • Bond pairs: 5
  • Lone pairs: 0
55
Q

Describe the pyramidal shape

A
  • Angle: 107
  • Bond pairs: 3
  • Lone pairs: 1
56
Q

Describe the trigonal planar shape

A
  • Angle: 120
  • Bond pairs: 3
  • Lone pairs: 0
57
Q

Describe the non-linear shape shape

A
  • Angle: 103.4
  • Bond pairs: 2
  • Lone pairs: 2
58
Q

Describe the octahedral shape

A
  • Angle: 90
  • Bond pairs: 6
  • Lone pairs: 0

chemistry (37 decks)

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