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c1 - atomic structure Flashcards

1
Q

What does the periodic table show ?

A

-The periodic table shows us all the elements .
-There are over 100 elments .

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2
Q

What is an element ?

A

A substance made up of only one type of aotm .

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3
Q

What are compounds ?

A

Compounds contain two or more different elemnts chemically bonded .
-Combined in a fixed proportion .

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4
Q

Key fact about compounds .

A

Compounds usually have totally different properties from the elemts that theya re made from .
-If we want to separate a compound , back into its elemnts , we need to use a chemical reaction .

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5
Q

What is a mixure ?

A

We have different elemnnts or compounds which are not chemically combined togther
-If we want to sepearate a mixture , then we use physical techiniques rather than chemcil rections .

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6
Q

What is a molecule ?

A

A molecule has anyy elemnts chemically joined .

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7
Q

What does a chemical formula show ?

A

Tells us all the elents in a molecule and also the number of atoms in each eement .
-you cannot change the small number in a chemical formula as this producs a different molecule .

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8
Q

What is the law of conservation of mass ?

A

The total number of products formed in a reaction is equal to the total number of reactants .

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9
Q

Physical separations can be used to separate ?

A

Mixtures , but cannot be used for elements in a compound .

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10
Q

Gieva few examples of Physical separation techniques :

A

-Filitriation
Crystalisation .
-Distillation
-Chromatoraphy

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11
Q

When is fitiration used ?

A

Filtriation is used to separate an insoluble soild from a liquid .
(insoluble means solid won’t dissove in a liquid ) .

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12
Q

Conditions for filitration .

A

Solid and LIquid (check state symbolds)
-Need a filter funnel and filter paper .

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13
Q

Stage one of filitiration .

A

Pour mizure into filter paper .
-The liquid passes through the tiny pores in filter paper . (fitrate)

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14
Q

Stage two of filtiration .

A

HOwever solid material can’t pass through the filter paper and so is trapped . (residue)
-In the end liquid is separated form the soild .

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15
Q

When is crystalisation used ?

A

Used to separae a soluble solid from a liquid . Aqueous solution need (aq) check state symbols .

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16
Q

What is one way of doing crystalisation ?

A

-Leave the solution for a few days and water will evaporate leaving crystals of ur thing sodium chloride eg .

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17
Q

What to do if you want crysalisation to happen faster ?

A

-Heat the solution to evaportae out water .
-Bbe careful that the chemical we are trying to crystalise is not effected by the heating . Certain chemcials break down when heated .

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18
Q

What is simple distillation ?

A

Used to separate a liquid from a solid if we want to keep the liquid .

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19
Q

How does simple distialltion work ?

A

First we evaporate the liquid by heating ,
-We then condense the vapour by cooling

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20
Q

How does simple distillaiotn work ?

A

-Heat the solution
-vapour now rises up glass tube
-vapour now passes into the condeser (kept cold as cold water circulates the condseer ).

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21
Q

How does simple distillaton work (2) ?

A

-This mens vapour condenses turning vapour into a liquid .
-collect liquid in a beaker , Left with crystals of solid in a flask and liquid in a beaker .

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22
Q

What happens in fractional distilaiton ?

A

We sepeare a mixture of different liquids .
KEY POINT - these liquids must have different boiling points .

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23
Q

first stage of fractional distillation ?

A

1.Start by gently heaitng the mixtures .

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24
Q

second stage of fractional distillation ?

A

the liquids start to evaporate , But one with lower boiling point will evaporate more easily .

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25
third stage of fractional distillation ?
When the vapours hit the fractonationg column , they condense and drip back into the falsk . The lquids hthen evaporate agaon .
26
fourth stage of fractional distillation ?
The repeated evaporation and cndensation increasing the amount of lower boiling point chemical in the fractonaitng column .
27
fifth stage of fractional distillation ?
As warm vapours pass up the coluumn they reach the thermoemter and temperature of it begins to rise . -meaning a mixture of 2 different vapours are passing over the thermomeer .
28
sixth stage of fractional distillation ?
both vapours now pss into condenser and turn into a liquid . -comes a point where temperature on thermoemter reaches bioling point of first chemical and it stops rising .
29
seventh stage of fractional distillation ?
now only one chemical in the condenser , so this is collected in a beaker .
30
eighth stage of fractional distillaiton
then the temperture rises agaom until reaches boiling point of second chemical , colect this in a second beaker .
31
What is the porblem if the liquids have very similar points in fractional distillation ?
-much harder to sepearte the liquids , might need multiple rounds of fractional distillaition .
32
fractional distillaiton to purifhy large volumes of lquid ?
-Sme principle but also requires different equipment . .
33
dra and label simple and fractional distillaiton .
check sheet .
34
How does paper chromatogrpahy do ?
Allows us to separate substances based on their dffierent solubilities .
35
first stage of papepr chromatogrpahy .
take a piece of chromatography paper . -draw a pencil lne near th botom .
36
second stage of paper chromatogrpahy .
-put dots of our colours (substance) on a pencil line .
37
third stage of paper chromatogrpahy .
now put paper into solvent (a liquid that will dissolve substances ).
38
fourth stage of paper chromatogrpahy .
The solvent now makes it way up the paper and dissolves the ink and coloured dots , which are also carried by the paper .
39
Why is paper in chromatography called stationary phase and the solven called mobile phase ?
Paper called stationary pahse as it does not move . SOlvent called mobile pahse as it moves .
40
A pure compound ...
will produce a sinlge spot in all solvent ,
41
a compound in a mixture (mixture of colours )
may sepearate into a different spots depending on the solvent .
42
More soluble substances...
travel further up the paper .
43
Why do we draw the starting line un pencil ?
As if we draw the line in pen , the pen ink would also move up with the solvent effecting the results
44
How to figure out unknown substance using chromatogrpahy .
-normal process of chromtogrpahy , measure the distance mvoed by the unkwon chemical (distance from pencil line to center of dot.) -Measure the distancce moved by solvent . Calcualtre rf calue distance moved by substance / distanced moved by solvent . no untis . look up in data base to find substance ,.
45
Rf value facts .
Several substacnes may have the same Rf calue , some may need to be repeated using a diffeent solvent . If a substance has never been analysed before m ti willl have no rf value .
46
RQP for paper chromatogrpahy .
Sample of food chemicals , 4 known food coloruings (a -d)
47
First stage pf paper chromatogrpahy rp ?
draw a hroizontal pencil line 2cm from the bootm of paper .
48
Second stage of paper chromatogrpahy rp ?
Mark five pencils pots at equal spaces acroos line . -make sure there 1cm clear on each side of the paper .
49
Third stage of paper chromatogrpahy rp ?
use a capiallary tube to put a small spot of eak of the known colours and the unkown colours ontol pencil spot
50
fourth stage of paper chromatogrpahy rp ?
now pour waer into beaker depth of 1cm water in this case solven .
51
fifthstage of paper chromatogrpahy rp ?
attach a glass rod using tape and lower paper into a glass beaker ,bottom of paper should dip into water .
52
pencil line with psots must be above the surface of water why ?
or water will wash off the line .
53
the sides of the paper must not touch side walls why >
or it will interfere with the way water move s. -Put a lid on beaker , to reudce the amount of evaporation of he solven t .
54
sixth stage of paper chromatogrpahy rp ?
at this stage water moeves up paper and colours are carried with it remove paper when water travleld three quarters up it , -use a pencil to mark point how far water reached , Hang paper to dry .
55
where are the unkwon colours ..
the spots that line up with the unkwon colour is unkown colour .
56
what did greeks say atoms were ?
Atoms were tiny spheres that cannot be divided .
57
What happned in 1897 ?
Scientists discovered atoms contain tiny negative elexrons called electrons , -showed that atoms have an internal structure . Came to the invention of plum puddign model - ball of possitive charge with embedded negative elctrons .
58
What did scientists do to see i the plum pudding model was correct ?
Did the alpha scateeirng experiment .
59
What happened in the alpha scattering experimen t .
-scientits took a piece of gold foil , gold used as it can be hammered into very thing foil . -Then fire tiny positive alpha particles athe goild foil .
60
What was the first observation of alpha scattering model .?
-most atoms passed striaght thorugh gold foil without changing idrection . -meant atoms were mostly empty space . .
61
What was the second observation of the alpha scattering model ?
-some alpha particles were deflced , changed direction when passin thorugh the gold foil , -meant the center of the atom must have a positive chtge , particles that came close to his are reppelled and changed direction .
62
what was the third observtion of the aplha scatering model ?
-some alpha particles bounced striaght off gold oil , -meant center of atom mst have a great deal of mass , center called nucleus ,
63
what did scienits do when they found reuslt of alpha scattering model ?
scientists replaced with nuclear model . -empt space -tiny positve nucleus -around the egde , negative electrons .
64
What did Niels Bohr propose ?
He proposed electorns orbit the nucleus at specific distacnes , which was accepted by scienits . -now call thse "orbits" energy levels /shells .
65
what happened several years after niels bohr .
-posiitve charge in nuclues so tiny positive particles called protons . 20 years after James CHadwick said nucles also contains neutrols . soa toms have no overal chatge as number of protons is euqaal to number of electrons .
66
What is the radius of an atom.
1*power of minus ten .
67
what is the radius of a nuclues
1*ten to power of -14 .
68
stae relative mass and relatve charge of proton neutrol and electron .
check sheet .
69
What is the mass number ?
number of protons +neurons .
70
What is the atomic number ?
NUmber of portons which is equal to the number of electrons .
71
How do you work out the number of neutrons ?
Mass number - atomic number .
72
What are isotopes ?
-Isotopes are atoms of the same element with different number of neutrons . -All atoms of an elemn have the same number of protons .
73
What are ions ?
Ions are atoms which have gained an overrall charge . They have gained or lost electrons .
74
More about ions ?
Positiove ions have lost electrons . Negative ions have gained electrons (check sheet for an example ).
75
electrons exist in ...
energy levels . -each energy level holds a maximum number of electors .
76
1 st sheel holds two electrons what does the second and third shell hold what does the fourth shell hold ?
electrons .8 electrons 18
77
How do you work out wat group an elet is in by looking at the elctronic structure ?
the last number , if it is (2,6) last number shows it is in group 6 .
78
elements with full outer energy levels are found in ...
group 0 , noble gases .

Chemistry (20 decks)

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