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elements of life > structures and properties of bonded substances > Flashcards

structures and properties of bonded substances Flashcards

1
Q

how are ions held in ionic solids`

A

by opposite charges - each cation is attracted to several anions

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2
Q

what do the ions build up into

A

a giant ionic lattice

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3
Q

are the ions in fixed positions

A

yes

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4
Q

how is the sodium chloride lattice arranged

A

each Na+ is surrounded by 6 Cl- ions
each Cl- is surrounded by 6 Na+ ions
this adds up to an infinite series of attractions and repulsions

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5
Q

which are stronger attractions or repulsions

A

attractions

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6
Q

why do ionic solids have high mp and bp and are hard

A

due to the strong lattice arrangement

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7
Q

what does NaCl have a cubic shape

A

due to the cubic NaCl crystals

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8
Q

what happens when ionic substances dissolve in water

A

the ions become surrounded by water molecules and spread out through the water

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9
Q

what happens when NaCl dissolves in water

A

the dissolved Na+ and Cl- ions are regularly scattered anymore, they are scattered randomly through the water. both ions act independantly of each other

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10
Q

what is each ion surrounded by

A

water molecules.

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11
Q

describe water

A

polar with a bent shape. oxygen is more electronegative than hydrogen

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12
Q

how do ions dissolve in water

A

positive ends of the water are attracted to the negative ions and the negative ends of the water are attracted to the positive ions

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13
Q

why does hydration release energy

A

to compensate for the immense amount of energy needed to break the bonds within an ionic lattice

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14
Q

what happens to ionic substances in water

A

when dissolved, the positive and negative ions separate and behave independantly

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15
Q

what are ionic compounds at room temperature and pressure

A

solids

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16
Q

how is the ionic lattice arranged

A

consisting of repeating +ve and -ve ions in 3D and often form regularly shaped crystals

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17
Q

how is the ionic lattice held together

A

the electrostatic attraction of oppositely charged ions overcomes the repulsion of the same charge, holding together the ionic lattice structures

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18
Q

why do ionic compounds have high melting and boiling points

A

a large amount of energy is needed to overcome the electrostatic attraction forces and break the ionic bonds to pull the ions apart

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19
Q

what happens once an ionic compound has melted

A

the ions are free to move and then can carry charge and conduct electricity

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20
Q

when can ionic compounds conduct electricity

A

if molten or dissolved since the ions can move

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21
Q

what substances do ionic compounds dissolve in

A

soluble in polar substances

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22
Q

what is the difference between carbon dioxide and sillicon dioxide

A

both are in group 4 but carbon dioxide is a gas at room temperature and SiO2 is a hard solid with a high mp

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23
Q

why do CO2 and SiO2 have different physical properties even though they are in the same group

A

there is a difference between the bonding between carbon and oxygen and sillicon and oxygen

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24
Q

what type of compounds are SiO2 and CO2

A

covalent

25
Q

what type of bonds can carbon form and why

A

the small size of the carbon atom makes it possible for carbon to form double bonds with oxygen so carbon dioxide is composed of individual molecules

26
Q

why is carbon dioxide a gas at room temperature

A

the bonds between carbon dioxide molecules are weak so little energy is needed to separate individual molecules in the solid and liquid phases to form a gas.

27
Q

how many oxygen atoms does sillicon bond to

A

four oxygen atoms (larger than carbon atoms)

28
Q

what is quartz

A

an extended network of SiO4

29
Q

describe some properties of SiO2

A

because of its giant covalent structure, SiO2 is insoluble in water and has a high mp and bp. this is due to the strong covalent bonding which exists throughout the SiO2 structure. lots of energy needed to break bonds within the structure

30
Q

what are two types of covalent structures

A

covalent molecular/simple molecular
covalent network/giant covalent

31
Q

what are some properties of covalent molecular structures

A
  • consists of discrete molecules.
  • strong covalent bonds within the molecules/between atoms (intramolecular forces)
  • weak covalent bonds between the molecules (intermolecular forces)
  • some dissolve in organic solvents
32
Q

what do the strength of the IMF determine

A

the state of the substance

33
Q

what are some properties of covalent network structures

A
  • consists of a giant repeating lattice of covalently bonded atoms.
  • substances with network structures are insoluble
  • solids with high mp and bp
34
Q

give some names of diatomic molecules

A

hydrogen, oxygen, nitrogen, fluorine, and chlorine

35
Q

what is phosphorus (P4) made of

A

four phosphorous atoms

36
Q

what is sulfur (S8) made of

A

8 sulfur atoms in a ring

37
Q

what is similar about S8 and P4

A

both are soft, low melting solids

38
Q

describe the bonds in network structures

A

bonds between individual atoms are strong covalent bonds and a lot of energy is needed to pull the atoms apart to form a liquid or gas

39
Q

what is the structure of sillicon

A

every sillicon is bonded to four other sillicon atoms in a tetrahedral arrangement. the giant lattice repeats the structure indefinitely in all directions

40
Q

what are the two allotropes of carbon

A

diamond and graphite

41
Q

describe the structure of diamond

A

every carbon atom is joined tetrahedrically to four other carbon atoms by strong covalent bonds forming a giant lattice

42
Q

why is diamond hard

A

due to its highly symmetrical structure and strong C-C bonds

43
Q

what are industrial grade diamonds used for

A

on the tips of drills and crushed diamonds are used on high quality grinding and cutting wheels

44
Q

describe the structure of graphite

A

made up of giant flat layers of carbon atoms. each layer is a two dimensional network. in layers each carbon atom is joined by strong covalent bonds to 3 others forming rings containing 6 carbon atoms

45
Q

what are there extended delocalised electron clouds between the layers in graphite

A

only 3 of the four outer electrons of carbon are used to form the hexagonal rings. the 4th electron of each atom contributes to the cloud of delocalised electrons

46
Q

what do the delocalised electrons do in graphite

A

causes the layers to be held together relatively weakly. the delocalised electrons are not attached to any particular carbon atom and are free to move around over the layers

47
Q

why is graphite a good conductor of electricity

A

because of its delocalised electrons that are able to move through the structure and carry charge

48
Q

why dont most covalent substances conduct electricity

A

all the electrons are held tightly in covalent bonds so they arent free to move from one molecule to the next through the structure

49
Q

give some properties of graphite

A

soft, brittle solid. the layers are bonded weakly to eachother so can slide over one another
used as a lubricant

50
Q

what are simple molecular substances soluble in

A

non polar solvents

51
Q

what are fullerenes

A

molecular form of carbon. dissolves in benzene to give a red solution.

52
Q

formula of fullerenes

A

C60

53
Q

what are the two types of fullerenes

A

buckminsterfullerene
nanotubes

54
Q

what is C60

A

optical limiter
shining light on a solution of C60 causes it to turn darker instantly and the more light there is the darker it gets so that the intensity of the transmitted light is limited to a maximum value

55
Q

describe metallic compounds

A
  • strong bonds in regular structures
  • high mp and bp
  • hard and strong
  • electrostatic forces acting in all directions
56
Q

how are metallic compounds formed

A
  • in a metal, atom loses several of its outer electrons which drift around the metal ion as delocalised electrons
57
Q

why are metallic compounds good conductors

A
  • good conductor of heat and electricity because of large number of free electrons
58
Q

why are metallic compounds malleable

A
  • regular structure means layers of atoms can fairly slide over eachother without breaking bonds so metals are malleable

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