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c2 Flashcards

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1
Q

Who was Mendeleev?

A

made first proper periodic table in 1869

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2
Q

how many electrons in each shell?

A

1st shell - 2 electrons
2nd shell - 8 electrons
3rd shell - electrons

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3
Q

what order did Mendeleev arrange the periodic table in?

A

order of atomic mass

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4
Q

how to work out electronic structure?
example of nitrogen

A

same amount of electrons as protons
e.g Nitrogen has 7 protons
so must have 7 electrons
2 electrons in 1st shell
7-2 = 5
5 electrons in 2nd shell
you write this as
2.5

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5
Q

how to work out electronic structure using period and groups?
example of sodium

A

.know the number of SHELLS which contain electrons is same as PERIOD
.group number tells you amount of electrons in outer shell
e.g NA period 3, group 1
3 electron shells
1 in the outer shell
1st shell always 2
2nd shell is full so 8
3rd shell has 1
so it has 11 electrons
electronic structure of 2.8.1

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6
Q

how are simple ions formed?

A

when electrons are lost or gained
ions are charged particles

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7
Q

which groups are most likely to form ions?

A

GROUP 1,2
GROUP 6,7

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8
Q

what Ions do group 1 and 2 become?

A

metals
lose ions to become positively charged
e.g NA+

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9
Q

What do ions with opposite charges form?

A

ionic bonds

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10
Q

how to find formula of an ionic compound?

A

balance positive and negative charges

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11
Q

Ionic compound of sodium chloride
NA+
CL-

A

NaCl

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12
Q

ionic compound of Potassium Oxide
K+
O2-

A

K20
need 2 K
to match with the O2-
K+ O2-
K+

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13
Q

what is the structure of ionic compounds?

A

regular lattice structure
.very strong electrostatic forces of attraction between oppositely charged ions

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14
Q

What are covalent bonds?

A

sharing electrons
.non-metal atoms combine they from covalent bonds by sharing pairs of electrons

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14
Q

properties of ionic compounds?

A

.high melting point
.high boiling point
due to strong attraction
.solid don’t conduct electricity
because ions are in a fixed place can’t move
.dissolve easily in water

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15
Q

Why do simple molecular substances have low melting and boiling points?

A

.atoms held together by strong covalent bonds
.very weak force of attraction between molecules
.melting and boiling points are low because it is easy to overcome the intermolecular force and SEPERATE THE MOLECULES

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15
Q

why are covalent bonds strong?

A

strong electrostatic attraction between positive nuclei of atoms and negative electrons

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16
Q

example of covalent bonds?

A

water
H2O
oxygen needs 2 more electrons to fill outer shell
.shares with 2 hydrogen atoms

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17
Q

properties of simple molecular structures?

A

.low melting point
.low boiling point
due to weak intermolecular forces
.don’t conduct electricity
don’t have free electrons
.most are gases and liquids at room temperature

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18
Q

what diagram is used to show ionic bonding?

A

dot and cross diagram

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18
Q

how to draw covalent molecules?

A

ball and stick model

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19
Q

what is a giant covalent structure?

A

.similar to giant ionic lattices except there are no charged ions
.atoms are bonded by strong covalent bonds
.very high melting and boiling points
.don’t conduct electricity

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20
Q

example of a giant covalent structure?

A

made from carbon
.diamond, graphite, graphene, fullerenes
.carbon atoms from up to 4 covalent bonds

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21
Q

giant covalent structures
DIAMOND properties

A

.lustrous, colourless
.carbon atom form FOUR covalent bond
.rigid giant covalent structure - so diamond is hard

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22
What is graphene?
a single sheet of graphite .so thin its transparent and light .even better at conducting electricity than graphite
22
giant covalent structures GRAPHITE AND GRAPHENE properties
.graphite is black and opaque - bit shiny .forms THREE covalent bonds .layers are weakly held together .graphite is a lubricating material .so graphite can conduct electricity
23
giant covalent structure .how many of carbons outer electrons form covalent bonds in GRAPHITE
.each carbon atom only forms THREE covalent bonds
24
giant covalent structures .how many of carbons outer electrons form covalent bonds in DIAMOND
.carbon atom form FOUR covalent bond
25
why does diamond have a high melting point?
.strong covalent bonds take a lot of energy to break so diamond has a high melting point
26
Why doesn't diamond conduct electricity?
no free electrons
27
Why does graphite have a high melting point?
covalent bonds require a lot of energy to break
28
Why can graphite conduct electricity?
.since only 3 out of each carbons four outer electrons are used to bond - means there is lots of DELOCALISED electrons .so graphite can conduct electricity
29
What is FULLERENES?
.another form of carbon . large carbon molecules
30
why can fullerenes conduct electricity?
it has delocalised (free) electrons
31
Why is fullerenes boiling point and melting point fairly high for a molecular substance?
big molecules so it has a stronger intermolecular force
32
how many m in a nm?
1nm = 0.000000001
33
what ratio do nanoparticles have?
high SA to Volume ratio
34
example of nanoparticles?
fullerenes
35
how to work out SA to volume ratio?
SA ÷ volume
36
as particles decrease in size what happens to the SA in relation to volume?
increases
37
what is a catalyst?
a substance that speeds up a chemical reaction
38
what is plastic an example of?
a polymer
39
what is a polymer?
lots of monomers joined together
40
what holds atom together in a polymer chain?
strong covalent bonds
41
what are properties of plastic with weak intermolecular forces?
.chains are free to slide so …plastics are easily stretched …low melting point
41
what are properties of plastic with a strong intermolecular forces?
.higher melting points .rigid so can't be stretched as cross-links hold chain firmly together
42
properties of metals (electrons)
.outer electron of each atom can move freely .atoms become postie in a sea of delocalised electrons
43
properties of metals?
.high melting and boiling points .high density .strong but bendy and malleable .god conductors of heat and electricity
44
what do metals form when they react with oxygen?
metal oxide
45
high/low melting point in a metallic structure?
high
45
what is formed when metals mix with other elements?
alloys
46
high/low melting point in a simple covalent structure?
low
46
high/low melting point in an ionic structure?
high
47
high/low melting point in a giant covalent structure?
high
47
What are pure substances?
contain only one thing
48
how to test for purity?
using boiling and melting points .pure substances have a specific boiling and melting point .pure ice melts at 0 degree .pure water boils at 1000 degrees
49
What is simple distillation used for?
separating out solutions
50
simple distillation to get pure water from sea water practical method
1. pour seawater into a distillation flask 2. set up apparatus 3. heat distillation flask - part of solution with lowest boiling point will evaporate (water) 4. water vapour passes into condenser where it'll cool and condense, then flows into beaker to be collected 5. eventually ending up with just salt in the flask and pure water in the beaker
51
What is fractional distillation?
separates a mixture of liquids
52
fractional distillation for crude oil practical method
1. pour mixture into a flask, attach fractionating column and condenser 2. heat flask gradually different liquids will have different boiling points so will evaporate at different temperatures 3. liquid with lowest boiling point evaporates first 4. liquids with higher boiling point if they start to evaporate will only get pat way up tube before condensing down as its cooler at the top 5. first liquid has been collected increase temperature until next liquid can evaporate
53
What is filtration used for?
separating an insoluble solid from a liquid
54
55
practical for filtration?
filter paper into a funnel and pour mixture into filter paper .liquid will go through filter paper whilst solid won't pass through leaving behind a solid residue
56
what is crystallisation?
separating a soluble solid from a solution
57
practical for crystallisation; method?
1. pour solution into an evaporating dish, gently heat solution. some solvent will evaporate and solution will become more concentrated 2. when some solvent has evaporated OR crystals start to form, remove the dish from the heat and leave to cool 3. salt should start to form crystals as it becomes insoluble in cold highly concentrated solution 4. filter crystals out of the solution and leave them to dry
58
what is chromatography?
method to separate and identify the substances in a mixture
59
what are the 2 phases of chromatography?
.mobile phase .stationary phase
60
what is the mobile phase in chromatography?
.where the molecules can move .liquid or gas
61
what is the stationary phase in chromatography?
.where the molecules cannot move .solid or thick liquid
62
what is thin-layer chromatography? (TLC)
.mobile phase is a solvent .stationary phase is a thin-layer of solid
63
method for TLC?
1. draw a line near bottom of the plate - in PENCIL (as its insoluble) 2. put a spot of the mixture to be separated on the pencil line 3. put some solvent into a beaker. dip bottom of plate (not the spot) in the solvent 4. put a watch glass over the beaker to stop any solvent from evaporating away 5. solvent will start to move up the plate. when chemicals in mixture dissolve in the solvent, they will move up the plate too 6. you will see different chemicals in the sample separate out forming spots at different places on the e plate 7. remove plate from beaker before the solvent reaches the top. mark the distance the solvent has moved in PENCIL
64
TLC what does the amount of time the molecules spend in each phase depend on?
.how soluble they are in the solvent .how attracted they are to the stationary phase -high solubility in solvent will spend more time in mobile phase so will be caried further up the plate
65
What is paper chromatography?
similar to TLC .difference is the stationary phase is chromatography paper (or filter paper) .mobile phase is a solvent such as ethanol (same as TLC)
66
what is the result of chromatography analysis called?
chromatogram
66
what is an Rf value?
ratio between distance travelled by solute and distance travelled by solvent
67
how to find the distance travelled by solute?
measure from baseline to the centre of the spot
68
what formula do you use to find the Rf value?
distance travelled by solute --------------------------------------- distance travelled by solvent
69
why is chromatography often used?
.to see if a certain substance is present in a mixture .for purity tests a pure substance won't be separated by chromatography, will always move one blob, while a mixture produce multiple blobs
70
what is gas chromatography (phases)? (GC)
.more high-tech .used to analyse unknown substances .mobile phase is an unreactive gas- N .stationary phase is a thick liquid - oil
71
process of GC?
1. unknown mixture is injected into a long tube coated on inside with stationary phase 2. mixture moves along the tube with the mobile phase until it comes out the other end. 3. time it takes a chemical to travel through the tube is called the retention time 4. retention time is different for each chemical
72
what is the chromatogram for GC?
a graph each peak is a different chemical .x axis is retention time .relative area under peak show relative amount of each chemical in sample .pure substance would only have 1 peak
73
what is relative formula mass?
Mr compound - all Ar added together in a formula
73
what is relative atomic mass
Ar bigger number on periodic table .average mass of one aotm of the element
73
what is the displayed formula?
shows atoms and covalent bonds in a molecule as a picture. H H - C - H H 1 carbon and 4 hydrogens can use this to write molecular formula
74
what is a molecular formula?
shows number and type of atoms in a molecule CH4 methane contains 1 carbon and 4 hydrogen
75
what is the empirical formula?
simplest ratio of atoms . C2H6 empirical formula CH3

chemistry (4 decks)

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