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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

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
Why can barium sulphate only be used in barium meals
1- solutions of Barium ions are poisonous but BaSO4 is insoluble so forms suspension instead of solutions
26
Mg(OH) solubility
Sparingly soluble
27
BaSO4 Uses
``` 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 ```
28
Why acidify BaCl2 with dilute HCl before testing for sulphates ions
remove any sulfites and carbonates which also form white precipitates
29
Why can't use sulphuric acid to acidify before testing for sulphates ions
add extra sulphate ions (SO42-)
30
Group 2 reactions with hydroxides
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31
Group 2 Reactions with sulphates
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32
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33
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34
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36
Halogens colour and phase at room temp
Fluorine - pale yellow - gas Chlorine - green -gas bromine - red-brown - liquid iodine - grey - solid
37
Boiling point Trends of Halogens
1- Boiling points INCREASE DOWN group 7 2- INCREASE In VDWs as size of molecules and Mr increases 3-changes in physical states
38
Electronegativity
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
Halogens oxidising or reducing agents
Oxidising agents oxidise something and itself gains e- and are reduced
40
REACTIVITY as oxidising agents down group 7 halogens
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
A halogen X2 will displace a Halide x-
if the halide is below the halogen in the periodic table
42
Displacement reaction with Flourine
- fluorine oxidises water | - no colourless solution formed
43
Displacement reaction with Chlorine
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
Displacement reaction with Bromine
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
Displacement reaction with Iodine
won't displace chloride or bromide as Iodine (halogen) is above the halides
46
Displacement reactions colour changes with KX
Cl2 + Br- = colourless to orange Cl2 + I- = colourless to brown Br2 + I- = colourless to brown
47
Making bleach (sodium chlorate (1) solution) NaClO-
1- disproportionation- chlorine 2NaOH + Cl2 --> NaClO + NaCl + H2O conditions- dilute NaOH, room temp,
48
uses of bleach NaClO- sodium chlorate solution
- cleaning toilets - water treatment - bleach paper
49
Chlorine and water reaction
1- mixing water and chlorine Cl2 + H2O 2H+ + Cl- +ClO- 2-Sunlight decomposes Cl2 + H2O 2H+ + 2Cl- + 1/2O2
50
disproportionation
Cl2 is both oxidised and reduced
51
Mixing water with chlorine
Cl2 + H2O 2H+ + Cl- + ClO-
52
Water and chlorine decomposed by sunlight
Cl2 + H2O 2H+ + 2Cl- + 1/2O2
53
chlorination of water
chlorate (ClO- ) ions kill bacteria
54
advantages of chlorinating water
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
disadvantages of chlorinating water
1-irritates lungs causing breathing problesm 2-chemical burns to skins and eyes 3-chlorinates hydrocarbons which are carcinogenic
56
Flame tests for positive ions
``` 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
Test for NH4+ ammonium ions
``` 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
Test for sulphate ions (SO42-)
1- add dilute HCl 2- add BaCl2 solution 3- Positive white precipiate of BaSO4 Ba2+ + SO42- --> BaSO4
59
Test of hydroxide (OH-)
1- pH indicator 2- dip red litmus paper Positive (OH)= goes blue
60
Test for halide ions
``` 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
Test for carbonates (CO32-) ions
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
LItmus paper test for pH
``` Acid = red alkaline= blue ```
63
why litmus paper needs to be damp
ammonium Gas dissolves
64
why can't you use HCl instead of HNO3
AgNO3 would react with Chloride (Cl-) from HCl forming AgCl and HNO3 white precipitate
65
Halide redox
Halide reducing agent, reduces something by donating e- and is itself oxidised by losing e-
66
Reducing power of halides down group Reducing agent
``` 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
Reactions with sulphuric acid reactions
``` Flourine, Chlorine, Bromine and Iodine NaX + H2SO4 --> NaHSO4 + HX Bromine and Iodine 2HX + H2SO4 --> X2 + SO2 +2H2O Iodine 6HI + SO2 --> H2S + 3I2 + 2H2O ```
68
Half equations of sulfuric acid
2X- --> 2e- + 2e- | H2SO4 + 2H+ + 2e- --> SO2 + 2H2O
69
Fluorine reaction with sulphuric acid and products
NaF + H2SO4 --> NaHSO4 + HF | Products- WHITE steamy fumes of HF
70
Chlorine reaction with sulphuric acid and products
NaCl + H2SO4 --> NaHSO4 + HCl | Products- WHITE steamy fumes of HCl
71
Bromine reaction with sulphuric acid and products
``` NaBr + H2SO4 --> NaHSO4 + HBr 2HBr + H2SO4 --> Br2(g) + SO2 + 2H2O Products= 1-Steamy fumes of Orange HBr 2- choking SO2 3- yellow solid ```
72
Iodine reaction with sulphuric acid and Products
``` 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
TRENDS in reducing ability of halides
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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