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Chemistry Module 2 > 2.2.2 Bonding And Structure > Flashcards

2.2.2 Bonding And Structure Flashcards

1
Q

Ionic bonding

A

Electrostatic force of attraction between oppositively charged ions formed by electron transfer

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2
Q

When are ionic bonds stronger

A

When ions are smaller

When ions have higher charges

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3
Q

Structure of ionic bonds

A

Arranged in a regular 3d giant ionic lattice

Oppositively charged ions in a regular arrangement

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4
Q

Physical properties of ionic compounds

A

High melting points: strong electrostatic forces of attraction between oppositively charged ions in the lattice
Doesn’t conduct electricity when solid: ions are held together tightly in lattice and can’t move so no charge is conducted
Conducts when molten/in solution: ions are free to move to conduct electricity
Usually soluble in aqueous solvents

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5
Q

Covalent bonding definition

A

Strong electrostatic attractikn between a shared pair of electrons and the nuclei of thr bonded atoms

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6
Q

Dative covalent bond

A

When shared pair of electrons in the covalent bond come from only one of the bonding atoms
Direction of arrow shows direction of donation

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7
Q

Average bond enthalpy

A

Measurement of covalent bond strength

Larger the value the stronger the bond

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8
Q

Simple molecular

A

Intermolecular forces (induced dipole dipole, permanent dipole dipole, hydrogen bonds)

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9
Q

Examples of ionic bonding

A

Sodium chloride

Magnesium oxide

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10
Q

Covalent bonding

A 
Iodine
Ice
Carbon dioxide 
Water
Methane
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11
Q

Melting and boiling points of giant ionic

A

High

Giant lattice of ions with strong electrostatic forces between oppositely charged ions

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12
Q

Melting and boiling points of simple molecular

A

Low

Weak intermolecular forces between molecules

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13
Q

Ionic solubility in water

A

Generally good

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14
Q

Simple molecular solubility in water

A

Generally poor

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15
Q

Conductivity when solid ionic

A

Poor

Ions fixed in lattice so cant move

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16
Q

Conductivity when solid simple molecular

A

Poor

No ions to conduct and electrons are localised

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17
Q

Conductivity when molten ionic

A

Good

Ions can move

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18
Q

Conductivity when molten simple molecular

A

Poor

No ions

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19
Q

Linear molecule

A

2 bonding pairs
No lone pairs
Angle 180
Co2

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20
Q

Trigonal planar

A

3 bonding pairs
No lone pairs
Bond angle 120
BF3

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21
Q

Tetrahedral

A

4 bonding pairs
No lone pairs
Bond angle 109.5
SiCl4

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22
Q

Pyramidal

A

3 bonding pairs
1 lone pair
Bond angle 107
NCl3

23
Q

Non-linear

A

2 bonding pairs
2 lone pairs
Bond angle 104.5
OCl2

24
Q

Octrahedral

A

6 bonding pairs
No lone pairs
90 degrees
SF6

25
Q

How to explain shape of molecules

A

State number of bonding pairs and lone pairs
State that electrons pairs repel and try to get to a position of maximum repulsion
No lone pairs then electron pairs repel equally, lone pairs repel more than bonding pairs
State shape and bond angles

26
Q

How do lone pairs effect bond angles

A

Reduce them

By around 2.5 degrees

27
Q

electronegativity

A

the relative tendency of an atom in a covalent bond in a molecule to attract electrons in a covalent bond to itself

28
Q

most electronegative atoms

A

F
O
N
Cl

29
Q

electronegativity across a period

A 
increases
number of protons increase
atomic radius decreases 
shielding stays the same 
but electrons are more attracted to the nucleus
30
Q

electronegativity down a group

A

decreases
distance between nucleus and outer electrons increases
shielding of inner shell electrons increases

31
Q

compounds with similar electronegativity are usually what

A

covalent

as there is a small electronegativity difference

32
Q

formation of a permanent dipole

A

also known as a polar covalent bond
forms when the elements in the bond have different electronegativities
unequal distribution of electrons in the bond and produces a charge separation with delta plus and delta minus ends

33
Q

element with the larger electronegativity takes which symbol

A

delta minus

34
Q

what is a symmetrical molecule

A

all bonds identical and no lone pairs

35
Q

symmetrical molecules

A

will not be polar even if individual bonds within the molecule are polar
the dipoles will cancel out due to the symmetrical shape, there is no net dipole movement so the molecule is non-polar

36
Q

compound containing large differences in electronegativity will be what

A

ionic

37
Q

where do induced dipole-dipole interactions occur

A

between all molecular substances
in noble gases
never in ionic

38
Q

another name for induced dipole-dipole forces

A

London forces

39
Q

induced dipole-dipole forces formation

A

electrons are constantly and randomly moving
electron density fluctuates and parts of the molecule become more or less negative
this forms temporary dipoles, which induces dipoles to form in neighbouring molecules
induced dipole is always the opposite sign to the original one
uses delta plus and minus

40
Q

main factor affecting the size of london forces

A

more electrons
higher the chance of london forces forming
makes induced dipole-dipole forces greater so the boiling points are greater

41
Q

explanation for the increased boiling points down the halogens

A

increased number of electrons
in bigger molecules
causes increased size of london forces
this is why I2 is a solid and Cl2 is a gas

42
Q

explanation for the increased boiling points of the alkane homologous series

A

increasing number of electrons in the bigger molecules

increased size of the London forces between molecules

43
Q

how can the shape of the molecule affect the size of london forces

A

long chain alkanes have a larger surface area of contact between molecules for london forces to form
whereas branched alkanes have less area of contact so less london forces

44
Q

what affects the size of london forces

A

amount of electrons

surface area of contact between molecules

45
Q

where do permanent dipole-dipole forces occur

A

between polar molecules

46
Q

permanent dipole-dipole molecules

A

occur between polar molecules
stronger than london forces so compounds have higher boiling points
polar molecules aren’t symmetrical, have a permanent dipole and have a bond where there is a significant electronegativity difference between the atoms

47
Q

when does hydrogen bonding occur

A

in compounds that have a hydrogen atom attached to an electronegative atom (N,O,F)
must be a lone pair of electrons available
large electronegativity difference between the two atoms

48
Q

what must you show on hydrogen bonding

A

the lone pair
the delta plus and minus
bond angle is 180 on a hydrogen bond
must label the hydrogen bond

49
Q

which is the strongest type of intermolecular bonding

A

hydrogen bonding

then
permanent dipole-dipole
induced dipole-dipole

50
Q

why does water have a high boiling point

A

hydrogen bonding between the molecules

51
Q

examples of molecules that can form hydrogen bonds

A

alcohols
carboxylic acids
proteins
amides

52
Q

what are the 2 anomalous properties of water

A

solid form ice can float on liquid form water

high melting/ boiling point

53
Q

how can solid from ice float on liquid form water

A

as the hydrogen bonds means water can form an open lattice

molecules are held further apart and therefore ice has a lower density

Chemistry Module 2 (8 decks)

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