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Chemistry > 2a:bonding and structure > Flashcards

2a:bonding and structure Flashcards

1
Q

what are the types of strong chemical bonds?[3]

A

1.ionic
2.covalent
3.metallic

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2
Q

what is ionic bonding?

A

its when a metal atom reacts with a non metal atom and electrons are transferred from the metal atom to the non metal atom which makes them oppositely charged ions which are strongly attracted to each other and the strong electrostatic attraction holds the ions together in the ionic compound

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3
Q

what do non metals atoms become during ionic bonding?

A

non-metal atoms gain electrons and become negatively charged ions with a full outer shell

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4
Q

what do metal atoms become during ionic bonding?

A

metal atoms lose electrons to become positively charged ions with a full outer shell

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5
Q

how can ionic bonding be represented?

A

dot and cross diagrams

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6
Q

what are ions?

A

charged particles

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7
Q

why are ions formed?

A

to get a full outer shell like a nobel has(to have a stable electronic structure)

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8
Q

what charge of ions do group 1 elements form?

A

1+ ions

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9
Q

what charge of ions do group 2 elements form?

A

2+ ions

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10
Q

what charge of ions do group 6 elements form?

A

2- ions

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11
Q

what charge of ions do group 7 elements form?

A

1- ions

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12
Q

what is an ionic compound?

A

a giant structure of ions held together in a lattice by strong electrostatic forces(ionic bonds) of attraction between oppositely charged ions.

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13
Q

what are the pros and cons of using dot and cross diagrams for ionic compounds?

A

useful for showing how ionic compounds are formed

don’t show the structure of the compound,relative sizes of the ions or how they’re arranged

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14
Q

what are the pros and cons of using 3d models to represent ionic compounds?

A

show the relative sizes of the ions and the regular pattern in an ionic crystal

only lets you see the outer layer of the compound

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15
Q

what are the pros and cons of using ball and stick models to represent ionic compounds?

A

shows the regular pattern in an ionic lattice
shows how the ions are arranged suggests the crystal extends beyond what is shown
may shows the relative size of the ions

sometimes ions are not shown to scale
suggests there are gaps between ions when there isn’t

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16
Q

how would you find the empirical formula from a dot and cross diagram?

A

count how many atoms there are of each element(so if there two chlorine atoms and one calcium atom then its CaCl2)

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17
Q

how would you find the empirical formula from a 3d model or a ball and stick model?

A

you need to balance the charges of the ions so the overall charge of the compound is zero.
eg.Na+ has a 1+ charge and Cl- has a 1- charge so you only need one of each ion to balance the charges so the empirical formula is NaCl

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18
Q

why do ionic compounds have high m.p and b.p?

A

they are giant structures with strong electrostatic forces of attraction between oppositely charged ions so large amounts of energy is needed to the break the many strong bomds

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19
Q

are ionic compounds soluble?

A

most ionic compounds dissolve easily in water

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20
Q

do ionic compounds conduct electricity?

A

not when solid because the ions are all held in fixed positions but when melted or dissolved,the ions are free to move and they’ll carry electric charge

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21
Q

when is a covalent bond formed?

A

when a pair of electrons are shared between two non metal atoms

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22
Q

why do atoms share electrons?

A

to get a full outer shell

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23
Q

why are covalent bonds strong?

A

the positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces which makes covalent bonds strong

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24
Q

how can you represent covalent bonding?[3]

A

1.dot and cross diagrams
2.displayed formula
3.3d models
4.stick and ball models

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25
what are the limitations of using dot and cross diagrams for covalent bonding?
useful for showing which atoms the electrons in covalent bond come from don’t show the relative sizes of the atoms or bow the atoms are arranged in space
26
what are the limitations of using displayed formulas for covalent bonding ?
useful for showing how atoms are connected in large molecules. don’t show the 3d structure of the molecule or which atoms the electrons in the covalent bond have come from
27
what are the limitations of using 3d model for covalent bonding?
shows the atoms and their arrangement in space can get confused for large molecules where there are lots of atoms to include and don’t show where the electrons in the bonds have come from
28
how could you find molecular formulas of a simple molecular compound from a given diagram for covalent bonding?
counting how many atoms there are of each element
29
what are simple molecules made up of?
a few atoms joined by covalent bonds
30
what are examples of simple molecules?
hydrogen,hydrogen chloride,methane,ammonia,water
31
what are examples of simple molecules that often form a single covalent bonds?
hydrogen(H2),Chlorine(Cl2),
32
how many covalent bonds are there in Methane and why?
4 because carbon has four outer electrons and hydrogen has 1 and only need to form one covalent bond to achieve a full outer shell. So carbon would form a covalent bond with 4 hydrogen atoms to form methane molecule.
33
what molecules have a double bond?
oxygen
34
what molecule has a triple bond?
nitrogen
35
how electrically conductive are covalent substances made up of simple molecules and why?
don’t conduct electricity because there are no ions or free electrons so there’s nothing to carry an electrical charge
36
what is the m.p and b.p of covalent substances made up of simple molecules and why?
low m.p and b.p because although the atoms within the small molecule form strong covalent binds the intermolecular forces are weak.Its the intermolecular forces that have to overcome to melt or boil a simple molecular force and it doesn’t take much energy to overcome them so the m.p and b.p are low
37
what is the trends in m.p and b.p in covalent substances made up of simple molecules?
as molecules get bigger,the intermolecular forces get stronger so more energy is needed to break them so the m.p and b.p increase
38
what does a polymer consist of?
lots of long molecules made up of repeating sections and all the atoms im a polymer molecule are joined by strong covalent bonds
39
when are polymers formed?
when lots of small units link together eg.many ethene molecules can be joined up to produce polythene
40
how can polymers be represented?
you can draw the shortest repeating unit ,put it in large brackets and put an n after the brackets.
41
how do you write the molecular formula of a polymer?
write down the molecular formula of the repeating unit by counting the number of atoms of each element,pit brackets around it and put an n after. eg.ethene is C2H4 so polythene is (C2H4)n
42
what is the m.p and b.p of polymers(compared to other bonds) and why?
higher m.p and b.p than simple covalent bonds because the intermolecular forces between the polymer molecules are stronger so more energy is needed to break them.However,their intermolecular forced are still weaker than ionic or covalent bonds so they generally have lower m.p and b.p
43
how are the atoms in macromolecules bonded to each other?
all the atoms are bonded to each other by strong covalent bonds
44
examples of macromolecules
diamond,graphite and silicon dioxide(silica)
45
do macromolecules have high m.p and b.p and why?
to melt a giant covalent molecule you need to overcome the strong covalent bonds which takes a lot of energy so the m.p and b.p are high
46
examples of larger covalent substances
1.polymers 2.giant covalent structures
47
how many covalent bonds does each carbon atom form with other carbon atoms in diamonds?
4
48
what are the properties of diamond?
forms a very rigid structure high m.p and b.p doesn’t conduct electricity
49
why does diamond have a high m.p and b.p?
the strong covalent bonds between atoms take a lot of energy to overcome
50
why do you need to overcome the covalent bonds instead of the intermolecular forces to melt or boil diamonds?
diamond is a giant covalent structure so you need to overcome their covalent bonds
51
why doesn’t diamond conduct electricity?
no free electrons or ions
52
how many covalent bonds does each carbon atom form in graphite and what does that create?
3 which creates sheets of carbon atoms arranged in hexagons
53
why can the sheets of graphite move over each other?
there aren’t covalent bonds between the layer,they’re held together by weak intermolecular forces
54
what are the properties of graphite?
high m.p and b.p soft and slippery(ideal as lubricant) conducts electricity
55
what can be said about graphites m.p and b.p?
high because the covalent bonds in the layers need a lot of energy to break
56
why can graphite conduct electricity?
only 3/4 of each carbons four outer electrons are used in bonds so each carbon atom has one delocalised electron and can move so graphite can conduct electricity and thermal energy
57
what does the electrical conductivity depend on?
whether or not there are ions that can move or free electrons that can move
58
what is graphene?
a sheet of carbon atoms joined together in hexagons
59
how thick is the sheet of graphene?
an atom thick
60
why can graphene conduct electricity?
contains delocalised electrons so can conduct electricity through the whole structure
61
what are the properties of graphene?
strong light conducts electricity
62
why is graphene strong?
the network of covalent bonds
63
what are fullerenes?
hollow molecules of carbon shaped like tubes or balls
64
what was the first fullerene discovered?
buckminsterfullerene(which is spherical)
65
what are the structures of fullerenes based on?
hexagonal rings of carbon atoms but they may contain rings with five or seven carbon atoms
66
whatever are carbon nanotubes?
cylindrical fullerenes with very high length to diameter ratio who are good conductors of heat and electricity
67
what can fullerenes be used for?[5]
1.medicine 2.as catalysts 3.as lubricants 4.strengthening materials 5.in electronics
68
how can fullerenes be used in medicine?
the fullerene structure forms around another atom or molecule which is then trapped inside and can be used to deliver drugs to where they’re supposed to go in the body
69
how can fullerenes be used as catalyst ?
high SA so could help make great industrial catalysts-individual catalyst molecules can be attached to the fullerenes
70
how can fullerenes be used as lubricants ?
coating moving machine parts in fullerenes reduces friction which may one day be used to reduce friction in artificial joints
71
how can fullerenes be used to strengthen materials?
nano tubes have a high tensile strength so can be used to strengthen materials without adding much weight (like tennis racket frames)
72
how can fullerenes be used in electronics ?
nanotubes can conduct electricity and they’re small so they can be used in electrical circuits (eg in microchips)
73
what do metals consist of?
giant structures of atoms arranged in a regular pattern
74
how does metallic bonding come to be?
the electrons in the outer shell of metal atoms are delocalised so they can move freely through the whole structure.There are strong forces of electrostatic attraction between the positive metal ion and the negative electrons and these forces(metallic bonding)holds the metal structure together
75
what are the properties of metals?
high m.p and b.p electric and thermal energy conductivity malleability
76
why do metals have high m.p and b.p?
the electrostatic forces between the metal atoms and the delocalised sea of electrons are so strong so there needs to be lots of energy to be broken
77
why can metals conduct electricity?
they have delocalised electrons that are free to move which can carry electric charge or the thermal energy through the whole metal structure
78
why are metals malleable?
metals consist of atoms held together in a regular structure which dorm layers that are able to slide over each other which means they’re malleable
79
what is an alloy?
a mixture of two or more metals or a metal and another element eg.brass is copper alloyed with zinc
80
why are alloys made?
they are harder so more useful than pure metals
81
why are alloys harder than metals?
when an element is mixed with a pure metal the new element atoms will distort the layers of metal atoms so its harder for them to slide over each other

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