topic 1 - atomic structure and the periodic table of elements

Question 1

give an example of a mixture

Answer 1

air - made of gases, nitrogen , co2 , oxygen , argon
crude oil
iron powder and sulfur powder, shows grey porperty of iron and yellow from sulfur

Question 2

describe the steps for the chromatography practical

Answer 2

1. draw a line near the bottom of a sheet of filter paper with a pencil.
2. add a spot of ink onto the line and place the sheet in a beaker of solvent.
3. the solvent used depends on whats being tested . some compounds require ethanol
4. make sure the ink isnt touching the solvent.
5. place a lid ontop of the container to stop the solvent evaporating.
6. the solvent seeps up the paper carrying the ink with it.
7. each different dye in the ink will move up the paper at a different rate so the dyes will seperate out.
8. if any dyes are insoluble it will stay onthe baseline
9. when the solvent has nearly reached the top , take the paper out of the beaer and leave to dry .
   the end pattern is called a chromatogram

Question 3

describe the method of filtration

Answer 3

used to seperate out insoluble solids from liquids
fold filter paper into a cone and place in funell.
the solid is left in the filter paper and liquid collected in a conical flask

Question 4

what are the two ways that you can seperate soluble solids from solutions

Answer 4

evaporation
1. pour the solution into an evaporating dish
2. slowly heat the solution. the solvent will evaporate and the solution will get more concentrated. eventually crystals will start to form.
3. keep heating the evaporating dish untill all you have left is dry crystals.

crystalisation ( used for if salt decomposes when heated )
1. pour the solution into an evaporating dish and gently heat the solution. some of the solvent will evaporate and the solution will get more concentrated.
2. once some of the solvent has evaporated , or when it reaches the point of crystalisation, remove the dish from the heat and leave to cool.
3. salt should start to form crystals as it becomes insoluble in the cold highly concentrated solution.
4. filter the crystals , wash and dry

Question 5

how can filtration and crystallisation be used to seperate rock salt

Answer 5

1. rock salt is a mixture of sand and salt.
2. salt and sand are both compounds - salt is soluble whereas sand isnt.
3. grindthe mixture to make the salt crystals small enough to dissolve.
4. put mixture in water and stir.
5. filter out the sand
6. evaporate the water from the salt to form dry crystals

Question 6

describe the steps to carry out distillation

Answer 6

simple distillation is used for seperating out a liquid from a solution
the solution is heated. the part of the solution that has the lowest boiling point evaporates first.
the vapour is then cooled, condenses in the condenser and is collected
the rest of the solution is left behind in the flask .
you can use simple distillation to get pure water from sea water. the water evaporates and is condensed and collected. eventually you will end up with just the salt left in the flask .
the problem is that it can only seperate things with very different boiling points.

Question 7

describe the process of fractional fdistillation

Answer 7

for seperating a mixture of liwuids
put mixture in a flask and stick a fractionating collumn on top . heat it
the different liquids hae different boiling points so they will evaporate at different temperatures .
the liquid with the lowest boiling point evaporates first. when the temperature on the thermometer matches the boiling point of this liquid , it will reach the top of the collumn.
liquids with higher boiling points might also start to evaportt.
but the column is cooler towards the top so they will only get part of the way up before condensing and running back down to the flask .
when the first liquid is collected, you rais the temperature untill the next one reaches the top.

Question 8

what are compounds

Answer 8

substances formed from two or more elements, the atoms of each are in fixed proportions throughout the compounf and they are held together by chemical bonds .

Question 9

what does making bonds involve

Answer 9

atoms giving away , taking or sharing electrons

Question 10

what ions to metals and non metals form

Answer 10

metals - positive
non metals - negative

Question 11

what are the chemical formulas for each of these compounds
carbon dioxide
ammonia
water
sodium chloride
carbon monoxide
hydrochloric acid
calcium chloride
sodium carbonate
sulfuric acid

Answer 11

co2
NH3
H2O
NaCl
CO
HCL
CaCl2
Na2 co3
H2 so4

Question 13

what determines what element an atom is

Answer 13

number of protons

Question 14

what is the equation for relative atomic mass of isotopes

Answer 14

sume ( isotope abundance x mass number ) / sum of abundances of all isotopes

Question 15

what is an isotope

Answer 15

different forms of the same element which have the same number of protons but different number of neutrons

Question 16

what is the size of the radius of an atom

Answer 16

o.1 nano metres
1 x 10 -10

Question 17

describe everything about the nucleus

Answer 17

made of protons and neutrons
radius of 1 x 10 -14 m
has positive charge
almost te whole mass of the atom is concentrated in the nucleus

Question 18

describe everything about electrons

Answer 18

move around the nucleus in shells
negatively charged , tiny
colume of orbits determine on size of the atom
virtually no mass

Question 19

what are the relative masses and charges of protons neutrons and electrons

Answer 19

proton - relative mass ; 1 , charge , 1
neutron - relative mass; 1 , charge , 0
electron - relative mass ; 0 , charge -1

Question 20

what aregroup 0 elements called and why

Answer 20

noble gases they are stable as they have 8 electrons in their outer shells

Question 21

describe the properties of the halogens

Answer 21

fluorine , very reactive poisonous yellow gas
chlorine - reactive poisonous green gas
bromine - demse, poinsonous , red brown volatile liquid
iodine - dark grey crystaline solide , or purple vapour

all exist as molecules (pairs of atoms )

as you go down the group:
they become less reactive - its harder to gai nan extra electron because the outer shell is further away from the nucleus .
have higher melting and boiling points
have higher relative atomic masses

react in similar ways as they all have seven electrons in their outer shells

Question 22

describe the properties of the noble gases

Answer 22

monatomic gases - single atoms not bonded to each other
colourlesss gases at room temperature
inert , non flammable

boiling point increases as you move down thhe group along with inceasing relative atomic mass
the increase in boiling point is due to an increase in number of electrons leading to greater intermolecular forces between them which need to be overcome

Question 23

what ions do halogens form

Answer 23

1 -
called halides

Question 24

describe all the properties of group 1 elements

Answer 24

alkali metals
have one electron in their outer shell which makes them very reactive
soft and have low density

as you go down the group :
reactivity increases- the outer electron is more easily lost as the attraction between the nucleus and electron decreases, because the electron is further away from the nucleus the further down the group you go
lower melting and boiling points
higher relative atomic mass

form 1 + ions
only form ionic compounds - white solids that dissolve in water to form colourless solutions

Question 25

how do group 1 metals react with water

Answer 25

they react vigorously to produce hydrogen gas and metal hydroxides - compounds that dissolve in water to produce alkaline solution s the more reactive an alkali metal is , the more violent the reaction the amount of energy given out by the reaction increases down the group - the reaction with pottasiu, releases enough energy to ignite hydrogen

Question 26

how do group 1 metals react with chlorine

Answer 26

react vigorously when heated with chlorine gas to form white metal chloride salts as you go down the group the reaction gets more vigorous

Question 27

how do group 1 metals react with oxygen

Answer 27

form metal oxide lithium reacts to form lithium oxide sodium reacts to form a mixture of sodium oxide and sodium peroxide potassium reacts to form a mixture of potassium peroxide (K2O2) and potassium superoxide (KO2)

Question 28

how are group 1 metals different rto transition metals

Answer 28

more reactive less dense, strong and hard lower melting point

Question 29

what are the properties of metals

Answer 29

strong , malleable conduct heat and electricity high boiling and melting points

Question 30

what are properties of non metals

Answer 30

dull brittle not always solid at room temperature dont conduct electricity low density

Question 31

what are properties of transition metals

Answer 31

can have more than one ion often coloured make good catalysts

Question 32

what were the two ways that elements used to be categorized

Answer 32

1. physical and chemical properties atomic weight

Question 33

what did dimitri mendeleev do

Answer 33

1869 - overcame some problems of the early periodic tables by taking 50 known elements and arranging them into his table of elements he put the elements in order of atomic weight but did switch that order if the properties meant it should be changed. gas were left to make sure that elements with similar properties stayed in the same groups. some of these gaps indicated the existance of undiscovered elements and allowed mendeleev to predict what their properties might be. the discovery of isotopes in the early 20th century confirmed that emndeleecv was correct not to place elements in a strict order of atomic weight but to also take account of thier properties

Question 34

describe the history of the atom

Answer 34

19th century - john dalton describe atoms as solid spheres and said different spheres made up the different elements 1897 - jj thomson concluded from his experiments that they werent solid spheres. he came up with the plum pudding model which was a bll of positive matter with negative electrons inside it. 1909 ernest rutherford - conducted the alpha particle scattering experiments . fired positively charged alpha particles at a thin sheet of gold. They expected that the particles would go straight through it as the positive charge from the plum pudding model was though to be very spread out. more than expected were deflected backwards . came up with the nuclear model , tiny , positively charged nucleus at the centre , where most of the mass is concentrated . a cloud of negative electrons surround the nucleus . most of the atom is empty space niels bhor s nuclear model suggested that electrons were in fixed shells . further experiments from rutherford shows that the nucleus can be divided into smaller particles . 20 years ;ater, james chadwick carried out experiments which proved that there were neutrons.