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Chemistry > BONDING< STRUCTURE< PROPERTIES OF MATTER > Flashcards

BONDING< STRUCTURE< PROPERTIES OF MATTER Flashcards

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1
Q

can ions be groups of atoms

A

yes eg NO¬3-

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2
Q

describe how an ionic bond is formed
3 points

A

(a metal and non metal react)
metal loses outer electrons & forms + charged ion
non-metal gains outer electrons and forms - charged ion
oppositely charged ions are strongly attracted by electrostatic forces
(this attraction is called ionic bond.)

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3
Q

define ionic bond

A

the attraction between electrostatic charges of newly formed ions

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4
Q

name for positive ion

A

cation

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5
Q

name for negative ion

A

anion

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6
Q

why do atoms lose/gain electrons

A

to get the electronic structure of a noble gas
(- stable electronic structure)

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7
Q

elements in which groups most readily from ions

A

1,2,6,7

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8
Q

what do you need to include when drawing a dot and cross diagram for ionic bonding
4 things

A

only outer electrons

square brackets around the element symbol once they become ions

charge of ion

how many electrons are in each shell in brackets
eg (2,8)
4 things

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9
Q

what structure do ionic compounds have

A

giant ionic lattice structure

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10
Q

limitations of dot and cross diagram for ions x3

A

don’t show structure of ionic compound
dont show size of ions
dont show how ions are arranged

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11
Q

what is an ionic compound

A

a giant structure of ions

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12
Q

describe what an ionic compound is like inside.
4 points

A

-giant ionic lattice structure

-ions form closely packed regular lattice

  • compound held together by strong electrostatic forces of attraction between oppositely charged ions.
    (this is ionic bonding)

-these forces act in all directions in the lattice

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13
Q

what are limitations of ball and stick /
2d/3d diagrams of ionic compounds

A

ball and stick-
-model isn’t to scale
-in reality there arent gaps between ions

2/3d diagrams
-only see outer layer of compound
-not to scale
- no info about movement of electrons to form ions

2d
doesnt show where ions are located on other layer

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14
Q

4 properties of ionic compounds

A

-high melting point
-high boiling point
-cant conduct electricity when solid
-can conduct electricity when melted or dissolved(in water)

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15
Q

why do ionic compounds have high melting/ boiling points

why do ionic compounds conduct electricity when melted/ dissolved in water

A

large amounts of energy needed to break the strong bonds between ions
melted/ dissolved- ions are free to move, so they’ll carry an electric charge

dissolved- ions separate, free to move in solution

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16
Q

example of a crystal that is one giant ionic lattice

A

sodium chloride (table salt)

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17
Q

how do you work out empirical formula from a 3d diagram and then from a dot and cross diagram
3 steps
remember in test to put working out on page/reasoning

A

work out what ions are in compound

work out what charges the ions will form

balance the charges so the charge of the empirical formula is 0

eg. potassium forms 1+ ion
oxygen forms 2- ion
need 2 potassiums to balance out the 2- charge of Oxygen

empirical formula is K¬2O

  • for dot and cross, count number of atoms of each element
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18
Q

covalent bonds are made when…

A

the + charged nuclei of the atoms attracted to the shared pair of electrons by electrostatic forces
this makes the covalent bonds strong

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19
Q

where does covalent bonds happen

A

in compounds of non metals and
in non metal elements

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20
Q

limitation of dot and cross diagram for covalent bonds

A

don’t show:
relative size of atoms
and
how atoms are arranged in space

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21
Q

limitations of displayed formula of covalent bonds
eg
H-N-H
a positive is it shows how atoms are arranged in large molecules

A

don’t show:
3d structure of molecule
or
which atoms the electrons in the covalent bond have come from

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22
Q

limitations of 3d model of covalent bonds x2

A
  • gets confusing for large molecules
  • don’t show where electrons in bonds have come from
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23
Q

how to find molecular formula of a simple molecular compound

A

count up how many atoms of each element there are eg C¬2H¬6

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24
Q

chemical formula for:
hydrogen
chlorine
oxygen
nitrogen
hydrogen chloride
methane
water
ammonia
* you need to be able to draw dot n cross for all of them

A

H¬2
Cl¬2
O¬2
N¬2
HCl
CH¬4
H¬2O
NH¬3

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25
Q

what type of structures do substances containing covalent bonds usually have

A

simple molecular structures eg O¬2, CH¬4

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26
Q

what are the properties of simple molecular substances
5 points

A

-atoms in a molecules held together by strong covalent bonds

(eg strong covalent bonds between 2 Oxygen atoms in a molecule of oxygen)

-weak intermolecular forces

(forces of attraction between molecules eg an O¬2 and another O¬2 molecule are weak )

-low melting and boiling points

-gas/liquid at room temp

-dont conduct electricity

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27
Q

what happens to bp and mp of simple molecular substances as the molecules get bigger. why

A

strength of intermolecular forces increases, more
energy needed to break the forces, mp and bp increase

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28
Q

why do simple molecular compounds/small molecules not conduct electricity

A

they are’nt charged, no free electrons/ions

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29
Q

explain how atoms are held together in a molecule of hydrogen chloride (covalently bonded)

A

a pair of electrons shared between atoms.
atoms held together by strong attraction between shared pair of - charged electrons and + charged nuclei of atoms

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30
Q

what are atoms in polymer molecules joined by

A

strong covalent bonds

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31
Q

describe the intermolecular forces between polymer molecules

A

intermolecular forces relatively strong-
stronger than in simple covalent,
weaker than ionic and covalent bonds

32
Q

what are polymers at room temp

A

solid

33
Q

when drawing the repeating unit of a polymer, what does the (…)n represent?
how do you find the molecular formula of a polymer

A

n - large number, unit repeated lots of times

  • look at the repeating unit.
    -write down molecular formula from that
    -put in brackets.
    -add n at the end
34
Q

describe the molecules in in polymers.

describe what a polymer is

A

very large molecules

-small units linked together, forms long molecule with repeating units/sections

35
Q

describe how atoms are bonded in a giant covalent strucutre

A

all atoms bonded to eachother by strong covalent bonds

36
Q

three main examples of giant covalent structures

A

graphite
diamond
silicon dioxide (silica)

37
Q

properties of giant covalent structures
and why
x2

A

high melting and boiling point
-lots of energy needed to overcome strong covalent bonds
don’t conduct electricity
- no charged particles

38
Q

what is an allotrope

A

different structure of same element in same state

39
Q

describe structure of diamond
x1

A

-each carbon atom has 4 covalent bonds with others

40
Q

describe structure of graphite
x4

A

each carbon atom covalently bonded to three others

  • layers of hexagonal rings
  • no covalent bonds between layers
  • one electron from each carbon atom is delocalised
41
Q

properties of diamond
x3

A

-really hard due to 4 covalent bonds
-high melting point
-doesnt conduct electricity

42
Q

properties of graphite
x3

A

-soft and slippery
-high melting point
-conducts electricity + thermal energy

43
Q

why is graphite soft and slippery

what is graphite ideal for?

why does graphite conduct electricity

A

-no covalent bonds between layers
-layers held together weakly
-layers free to move over eachother
* ideal as lubricating material
-each carbon atom has one delocalised electron

44
Q

what is graphene

A

(sheet of graphite)
-sheet of carbon atoms joined together in hexagons

45
Q

properties of graphene x4

A

-one atom thin (2d)
-strong due to covalent bonds
-light
-conduct electricity

46
Q

why is graphene useful

A

light- added to composite materials to improve strength without weight

conduct electricity through whole structure- useful in electronics

47
Q

allotropes of carbon

A

diamond
graphene
graphite
fullerene

48
Q

what are fullerenes

what was the first to be discovered and what was its shape

A

they are molecules of carbon with hollow shapes- (closed tubes/hollow balls

buckminsterfullerene- C¬60 -a sphere

49
Q

describe structure of fullerene

A

made of carbon atoms arranged in hexagons -6 atoms or also (pentagons) 5 atoms (heptagons) 7 atoms

50
Q

uses of fullerenes x4 and why x2

A

-to cage molecules- to deliver drug into body
why- forms around molecule and trap it inside

-industrial catalysts
why- large sa. so other catalysts can attach to the fullerenes

lubricant

strengthening materials

51
Q

what is a carbon nano tube

A

cylindrical fullerene with high length to diameter ratio

51
Q

what are carbon nanotubes useful for x3

A

nanotechnology ( technology that uses small particles)
electronics
materials- strengthen material without adding weight

52
Q

properties of nanotubes
x3

A

-high length to diameter ratio
-conduct electricity and thermal energy
-high tensile strength

53
Q

metals consist of….

A

giant structures of atoms arranged in a regular pattern

54
Q

describe the metallic bonding in metals and structure

A

-electrons in outer shells are delocalised
- free to move through strucutre
-strong electrostatic attraction between + metal ions and the sea of delocalised - electrons
-this force is a metallic bond
-strong metallic bonds hold atoms in REGULAR STRUCTURE

55
Q

substances held together by metallic bonds include….
ALL the properties of metals are due to….

A

elements and alloys
delocalised electrons (in metallic bonds)

56
Q

describe mp and bp of metals + why
what are most metals at room temp

A
  • high mp and bp
    -metals have giant strucutre of atoms with strong metallic bonds (between metal atoms and sea of delocalised electrons)
    -need alot of energy to break

solid

57
Q

are metals good conductors of electricity and heat? explain

A

-delocalised electrons carry electric charge and thermal energy
- through whole structure
- good conductors

58
Q

describe atoms in pure metals and effect of this

A

-atoms arranged in layers(that can slide over eachother)
-means metals can be bent and shaped ( malleable )

59
Q

properties of metals x3

A

malleable
good conductors
high melting/boiling point

60
Q

what are alloys
why are they made

A

a mixture of: 2 or more metals/ metal and another element
pure metals too soft for many uses. alloys are harder and more useful

61
Q

why are alloys harder than pure metals
3 points

A

-different elements have different size atoms.
-layers distorted when pure metal mixed with another element
- layers can’t slide over eachother

62
Q

The amount of energy needed to change state depends on ………
this then depends on

A

the strength of the forces between the particles of the substance.
the material, temperature, pressure.

63
Q

describe particles in solid
4 points

A
  • strong forces of attraction keeps particles
    -close together in fixed positions in a
    -lattice arrangement
  • solid has set shape and volume (as particles dont move)

-vibrate in fixed positions- more when solid is hotter
(causing solids to expand when heated)

64
Q

describe particles in liquids
4 points

A

-weak forces of attraction
-randomly arranged and free to move
-tend to stick closely together

-fixed volume, not shape ( will flow to fill bottom of container)

-constantly move in random motion- faster when liquid hotter
(liquids expand slightly when heated)

65
Q

describe particles in gases
4 points

A
  • weak forces of attraction
  • particles free to move + are far apart
    -travel in straight lines
  • no definite shape/ volume (fill any container)

-constantly move in random motion- faster when gas is hotter
( when heated, gases EITHER expand / pressure increases

66
Q

limitation of simple model of atoms in gas, liquid, solid
x3

A

-there are no forces in model ( so don’t know how strong they are)
-all particles represented as spheres
-spheres are solid.

67
Q

describe how solid becomes liquid and liquid becomes gas

A

solid/liquid heated
particles gain energy
vibrate more / faster
forces that hold solid/liquid are weakened/ broken
at melting point/ boiling point particles have enough energy to break free from position/ break bonds
change state to liquid/gas

68
Q

describe how gas becomes liquid and liquid becomes solid

A

gas / liquid cools and particles don’t have enough energy to overcome forces of attraction
bonds form/ more bonds form

at BP, so many bonds formed that gas becomes liquid- condensing
at MP, so many bonds form that particles held in place- liquid becomes solid- freezing

69
Q

nanoscience works with nanoparticles of what size
what is size of reular atoms

A

1 to 100 nm diameter
-few hundred atoms
1x 10¬-10 metres

70
Q

size of coarse particles
another name for coarse particles
size of fine particles

A

1 x 10¬-5 m and 2.5 x 10¬-6 m
aka dust
100 and 2500 nm

71
Q

what happens to s.a to vol ratio when size of atom decreases
if side of cube decreases by factor of 10, what happens to s.a to vol ratio

A

s.a to vol ratio increases as size decreases
side of cube decreases by factor of ten, s.a to vol ratio increases by factor of ten

72
Q

whats special about nanoparticles and explain
3 points

A

high s.a to vol ratio
properties of material different depending on if its a nanoparticle or in bulk
smaller quantities needed to be effective than materials with normal particle size

73
Q

uses of nanoparticles
x6

A

medicine- tiny so absorbed easily- deliver drugs right into cells
electronics- if the material conducts, used in tiny electric circuits for computer chips
cosmetics-improve moisturiser w/out making it oily
suncreams
deodrants
catalysts=large sa to vol ratio
(+clothes)

74
Q

disadvantages of using nanoparticles
x3

A

-the effects on health not yet properly investigated.(some believe nanoparticle products should be clearly labelled)

  • not clear if they get into body and damage cells- (Modern nanoparticulate materials have only common recently,hard to determine risks)

-when washed away / thrown away - may damage environment- eg silver nanoparticles may harm or kill useful bacteria in the environment

75
Q

why are nano particles used in suncreams
x2

A

better than traditional suncreams at protecting skin from harmful UV

better skin coverage

76
Q

why are nanoparticles used in medicine
2 main points

A

-tiny so absorbed easily, deliver drugs right into cells

-silver nanoparticles have antibacterial properties.

added to polymer fibres, then used for masks/ wound dressings

Chemistry (18 decks)

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