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Chemistry a level > U2,S1,S2-Periodicity, Group 2 and 7 > Flashcards

U2,S1,S2-Periodicity, Group 2 and 7 Flashcards

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1
Q

Atomic radius across period

A

1- Atomic radius decreases across period
2-As number of protons increases, +ve Nuclear charge increases
3-Electrons pulled closer to nucleus due to stronger electrostatic attraction.
4- Electrons added to outer energy level- so no shielding

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2
Q

Melting points across Period 3

A

Increase from Na to Si

General decrease from Si to Ar

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3
Q

Sodium, Magnesium and Aluminium MP

A

1- MP Increase across period as metallic bonds increase in strength
2-Increase across period as Metal ions increase in +ve charge
3- Increase in delocalised electrons
4-Decrease in atomic radius
5- Strong electrostatic attraction between Al3+ and 3e-

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4
Q

Silicon MP

A

1- Highest MP
2- Macromolecular with tetrahedral structure
3-lots of energy required to break covalent bonds

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5
Q

Phosphorus (P4), sulphur (S8), chlorine (Cl2) and argon (Ar)

A

1-Simple covalent molecular compounds
2-Weak VDWs forces between molecules
3-Low Mp
4-S8 is largest molecule so highest MP as most molecules so more stronger VDWs
5-Ar smallest molecule so lowest MP so very weak VDWs

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6
Q

First Ionisation energy Across period

A

1-General increase across period, increasing attraction between outer shell -ve electrons and +ve nucleus due to protons number/Nuclear charge increasing

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7
Q

First ionisation energy Al lower than expected

A

1-Al outer e-is in 3p sub-shell orbital that has higher energy than 3s sub-shell orbital so e- on average further from nucleus reducing electrostatic attraction.
2-3p orbital has additional shielding by 3s reduce Electrostatic attraction
3-Additional shielding and Increased atomic radius override Increasing nuclear charge

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8
Q

First ionisation energy S lower than expected

A

1- Identical shielding between P and S as e- is removed from same 3p sub-shell orbital
2- Sulphur (3p4) removed from an orbital with 2 e- which repel each other= weakens electrostatic attraction so easier to remove e- 3p4

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9
Q

Atomic radius down group 2

A

1-Increase atomic radius Down G2
2-Extra e- shells increasing shielding reducing electrostatic attraction
3-Increasing atomic radius
4- Override Increasing Nuclear charge/proton number so easier to remove e-

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10
Q

First ionisation energy down Group 2

A

1- 1st Ionisation energy Deceases down G2
2- Increased Shielding
3-Increased Nuclear radius
4- Decreasing electrostatic attraction as e- in outer shell are further away from positive nuclei
5- Overrides increasing Nuclear charge

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11
Q

Reactivity Down Group 2

A

1- Reactivity Increases Down Group 2
2-1st Ionisation energy decreases so easier to lose delocalised e- forming +ve ions making it more reactive
3- Increased atomic radius
4- Increased shielding
5- Overrides Increased Nuclear charge so it takes less energy to break metallic bonds as less electrostatic attraction

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12
Q

Melting points down Group 2

A

1-MP General decrease Down Group 2
2-Group 2 elements have metalic struture with +ve ions electrostatically attracted to delocalised e-
3- Metal ions get bigger DOWN G2 but number of delocalised e- per atom and ion charge don’t change
4-Atomic radius increases- further distance between outer shell delocalised e- and +ve nuclei
5- shielding increases
6- 1st ionisation energy decreases
7- Overrides increasing nuclear charge so less energy to break Metallic bonds

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13
Q

Oxidation of Group 2

A

1-M–>M2+ + 2e-

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14
Q

Group 2 reactions with water

A
  • Metal hydroxide and hydrogen
    M + 2H2O——> M(OH)2 + H2
    0 ——–> +2
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15
Q

Elements react more readily down G2

A

1st ionisation energy decreases so easier to remove e-

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16
Q

Solubility of compounds down group 2

A

1- Compounds that contain slightly -ve (OH-) charges INCREASE in solubility DOWN group 2
2- Compounds with doubly charges Ions (SO42-) charges DECREASE in Solubility DOWN Group 2

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17
Q

SOLUBILITY OF OH- down Group 2

A

OH- INCREASES in solubility DOWN Group 2

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18
Q

SOLUBILITY of SO42-

A

SO42- DECREASES in solubility DOWN Group 2

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19
Q

Why does Mg have a lower MP than expected down group 2

A
  • Crystal structure and arrangement of metallic Mg2+ ions changes so weaker metallic bonds as less electrostatic attractions
  • charges of 2+ and 2e- balance
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20
Q

Ca(OH)2 uses

A

agriculture to neutralise excess acidity in soils

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21
Q

Mg(OH) uses

A

antacid to neutralise excess stomach acid indigestion

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22
Q

Uses of CaCO3 and CaO

A

1-removal of SO2 from flue gases
2-Wet scrubbing = CaO + CaCO3 with water makes alkaline slurry
3- forms calcium sulfite CaSO3
CaO + 2H2O + SO2 –> CaSO3 + 2H2O
CaCO3 + 2H2O + SO2 –> CaSO3 + 2H2O + CO2

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23
Q

Extraction of Titanium

A

1-titanium(iv) oxide (TiO2) converted to titanium chloride (TiCl2) by heating it with Carbon in steam of chlorine (Cl2) gas
2- TiCl2 Purified by fractional ditillation and reduced by Mg in a 1000 degree furnace
2TiO2 + 3C +4 Cl2 —-> 2TiCl2 + CO2 + 2CO
TiCl4 + 2Mg —-> Ti + 2MgCl2

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24
Q

Barium meals (suspension of BaSO4)

A

1-Barium sulphate (BaSO4) is insoluble
2-Barium sulphate suspension swallowed
3-coats soft tissue and is opaque to x rays
4- Shows structure of soft tissues in x-ray

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25
Q

Why can barium sulphate only be used in barium meals

A

1- solutions of Barium ions are poisonous but BaSO4 is insoluble so forms suspension instead of solutions

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26
Q

Mg(OH) solubility

A

Sparingly soluble

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27
Q

BaSO4 Uses

A 
Used to test for sulphate SO42- ions
1-BaSO4 is insoluble 
2-add dilute HCL
3-add BaCl2 to solution of sulphate ions 
Positive= white precipitate of BaSO4
Ba2+ + SO42- ----> BaSO4
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28
Q

Why acidify BaCl2 with dilute HCl before testing for sulphates ions

A

remove any sulfites and carbonates which also form white precipitates

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29
Q

Why can’t use sulphuric acid to acidify before testing for sulphates ions

A

add extra sulphate ions (SO42-)

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30
Q

Group 2 reactions with hydroxides

A

ddd

31
Q

Group 2 Reactions with sulphates

A

ddddd

32
Q

hdhdhd

A

d

33
Q

dd

A

dddd

34
Q

dddd

A

dd

35
Q

dd

A

dd

36
Q

Halogens colour and phase at room temp

A

Fluorine - pale yellow - gas
Chlorine - green -gas
bromine - red-brown - liquid
iodine - grey - solid

37
Q

Boiling point Trends of Halogens

A

1- Boiling points INCREASE DOWN group 7
2- INCREASE In VDWs as size of molecules and Mr increases
3-changes in physical states

38
Q

Electronegativity

A

1-Electronegativity DECREASES DOWN group 7
2-size of molecules and Mr increases
3-larger atoms attract e- less than smaller ones
4- BECAUSE INCREASED Sheilding
5- INCREASED atomic radius
6-e- further from nucleus decreases electrostatic attraction so overrides increasing nuclear charge
7-reactivity DECREASES Down group

39
Q

Halogens oxidising or reducing agents

A

Oxidising agents oxidise something and itself gains e- and are reduced

40
Q

REACTIVITY as oxidising agents down group 7 halogens

A

1-Reactivity DECREASES down group 7
2- Atoms size and Mr INCREASES
3-Atomic radius INCREASES
4-Shielding INCREASES
5-Overrides increasing nuclear charge
6-Harder to gain electrons and get reduced so weak oxidising agent
7- weaker electrostatic attraction between outer e- and +ve nuclei

41
Q

A halogen X2 will displace a Halide x-

A

if the halide is below the halogen in the periodic table

42
Q

Displacement reaction with Flourine

A
  • fluorine oxidises water

- no colourless solution formed

43
Q

Displacement reaction with Chlorine

A

1- add chlorine (Cl2) to solution of bromide (Br-) ions, Chlorine (Cl2) will displace Bromide (Br-) ions
Cl2 + 2KBr –> 2KCl + Br2
Ionic- Cl2 + 2Br- –> 2Cl + Br2
Colour change- colourless to Orange (Br2) solution
2-add Chlorine (Cl2) to a solution of iodide (I-), Chlorine (Cl2) will displace iodide (I-) ions
Cl2 + 2KI –> 2KCl + I2
Ionic- Cl2 + 2I- –> 2Cl- + I2
Colour change- Colourless to Brown (I2) solution

44
Q

Displacement reaction with Bromine

A

1- add bromine (Br2) to a solution of Iodide (I-) ions, Bromine (Br2) will displace Iodide (I-) ions
Br2 + kI –> KBr + I2
ionic= Br2 +2 I- –> 2Br- + I2
colour change- Colourless to Brown (I2) solution

45
Q

Displacement reaction with Iodine

A

won’t displace chloride or bromide as Iodine (halogen) is above the halides

46
Q

Displacement reactions colour changes with KX

A

Cl2 + Br- = colourless to orange
Cl2 + I- = colourless to brown
Br2 + I- = colourless to brown

47
Q

Making bleach (sodium chlorate (1) solution) NaClO-

A

1- disproportionation- chlorine
2NaOH + Cl2 –> NaClO + NaCl + H2O
conditions- dilute NaOH, room temp,

48
Q

uses of bleach NaClO- sodium chlorate solution

A
  • cleaning toilets
  • water treatment
  • bleach paper
49
Q

Chlorine and water reaction

A

1- mixing water and chlorine
Cl2 + H2O 2H+ + Cl- +ClO-
2-Sunlight decomposes
Cl2 + H2O 2H+ + 2Cl- + 1/2O2

50
Q

disproportionation

A

Cl2 is both oxidised and reduced

51
Q

Mixing water with chlorine

A

Cl2 + H2O 2H+ + Cl- + ClO-

52
Q

Water and chlorine decomposed by sunlight

A

Cl2 + H2O 2H+ + 2Cl- + 1/2O2

53
Q

chlorination of water

A

chlorate (ClO- ) ions kill bacteria

54
Q

advantages of chlorinating water

A

1- kills microbes and bacteria
2-persists in water prevents reinfection further down stream
3-Prevents growth of algae bad taste
4- removes discoloration by organic compounds

55
Q

disadvantages of chlorinating water

A

1-irritates lungs causing breathing problesm
2-chemical burns to skins and eyes
3-chlorinates hydrocarbons which are carcinogenic

56
Q

Flame tests for positive ions

A 
1-wire dipped in conc HCl
2- add sample and heat in Bunsen
Calcium (Ca+) = brick red
strontium (Sr2+)= red
Barium (Ba2+) = pale green
57
Q

Test for NH4+ ammonium ions

A 
1- damp red litmus paper
NH4+ + OH- --> NH3 + H2O
2- add dilute NaOH
3- gently heat
Litmus paper goes blue as dissolves NH3 to paper
58
Q

Test for sulphate ions (SO42-)

A

1- add dilute HCl
2- add BaCl2 solution
3- Positive white precipiate of BaSO4
Ba2+ + SO42- –> BaSO4

59
Q

Test of hydroxide (OH-)

A

1- pH indicator
2- dip red litmus paper
Positive (OH)= goes blue

60
Q

Test for halide ions

A 
1- dilute (HNO3) nitric acid 
2- (AgNO3) silver nitrate solution 
Ag+ + X- --> AgX
F-=None Cl-=White ptt Br-=Cream ptt
I-= yellow ptt
3-add Ammonia (NH3) solution
Cl-= dissolves in dilute NH3
Br-= dissolves in conc NH3
I-= insoluble in conc NH3
61
Q

Test for carbonates (CO32-) ions

A

1-dilute HCl to carbonate solution
2-bubble gas through limewater
Positive= effervescence, CO2 released, limewater goes white milky/ cloudy
CO32- + 2H+ —> CO2 + H2O

62
Q

LItmus paper test for pH

A 
Acid = red
alkaline= blue
63
Q

why litmus paper needs to be damp

A

ammonium Gas dissolves

64
Q

why can’t you use HCl instead of HNO3

A

AgNO3 would react with Chloride (Cl-) from HCl forming AgCl and HNO3 white precipitate

65
Q

Halide redox

A

Halide reducing agent, reduces something by donating e- and is itself oxidised by losing e-

66
Q

Reducing power of halides down group Reducing agent

A 
1-Reducing power Increases DOWN Group 2
2-more easily oxidised loses e- easier 
3-Atomic Radius INCREASES
4-Shielding INCREASES
5- Weakens electrostatic attraction 
6-easier to remove electrons so easily oxidised 
7-Overrides Increasing Nuclear charge
67
Q

Reactions with sulphuric acid reactions

A 
Flourine, Chlorine, Bromine and Iodine
NaX + H2SO4 -->  NaHSO4 + HX
Bromine and Iodine
2HX + H2SO4 --> X2 + SO2 +2H2O
Iodine 
6HI + SO2 --> H2S + 3I2 + 2H2O
68
Q

Half equations of sulfuric acid

A

2X- –> 2e- + 2e-

H2SO4 + 2H+ + 2e- –> SO2 + 2H2O

69
Q

Fluorine reaction with sulphuric acid and products

A

NaF + H2SO4 –> NaHSO4 + HF

Products- WHITE steamy fumes of HF

70
Q

Chlorine reaction with sulphuric acid and products

A

NaCl + H2SO4 –> NaHSO4 + HCl

Products- WHITE steamy fumes of HCl

71
Q

Bromine reaction with sulphuric acid and products

A 
NaBr + H2SO4 --> NaHSO4 + HBr
2HBr + H2SO4 --> Br2(g) + SO2 + 2H2O
Products=  1-Steamy fumes of Orange HBr
                   2- choking SO2 
                   3- yellow solid
72
Q

Iodine reaction with sulphuric acid and Products

A 
NaI + H2SO4 --> NaHSO4 + HI
2HI + H2SO4 --> I2(s) + SO2 +2H2O
6HI + SO2 --> H2S + 3I2(s) + 2H2O
Products= 1- Purple gas 
                  2- Grey precipitate- Iodine
                  3- egg smell-H2S
73
Q

TRENDS in reducing ability of halides

A

F- and Cl won’t reduce concentrated sulphuric acid.

Bromide ions reduce the sulphuric acid to sulphur dioxide. In the process, the bromide ions are oxidised to bromine.

Iodide ions reduce the sulphuric acid to a mixture of products including hydrogen sulphide. The iodide ions are oxidised to iodine.

Reducing ability of the halide ions increases as you go down the Group.

Chemistry a level (22 decks)

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