Group 2 & Group 7 Flashcards

1
Q

Group 1 & Group 2 have the same trends

A
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2
Q

Atomic Radius

A
  • Down G2, INCREASES
    ↳ more QL = more electrons →electrons are further away : easier to remove
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3
Q

Ionisation Energy

A
  • Down G2, DECREASES
    ↳ more QL = further away electrons →easier to remove : less energy needed
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4
Q

Mp/Bp

A
  • Down G2, DECREASES
    ↳ atomic radius increases = outershell has lower nuclear charge (between cation & electron)
    ↳ less energy is needed to break this making the mp/bp lower
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5
Q

Reactivity to water

A
  • Down G2, increases
    ↳ atomic radius increases = outer electron is further away
    ↳ reacts w water easily
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6
Q

G2 react w water produce HYDROXIDES

A
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7
Q

G2 burn in oxygen forming OXIDES

A
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8
Q

G2 react w chlorine forming CHLORIDES

A
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9
Q

Trend

A

Every G2 elements form ionic bonds except Berilium which forms covalently
* BeO doesn’t react w water (exception)
* MgO reacts slowly w water

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10
Q

Down G2, reactivity increases

A
  • Alkaline solutions become stronger
    ↳ the hydroxide ions become more soluble
    -hydeoxides form more quickle : the pH of the solution goes above 7
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11
Q

G2 Oxides react w water

A
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12
Q

G2 Oxides react w dilute acid

A
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13
Q

Solubility Trend

Hydroxide

A

Down G2, increases in hydroxide ions (OH)
* more soluble : pH goes above seven
↳ meaning that it will dissolve faster

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14
Q

Solubility Trend

Sulfate

A

Down G2, decreases in sulfate ions (SOv4 -2)
* become less soluble
↳ dissolve slower

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15
Q

Thermal Stability

A

Applied heat needed to break something down

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16
Q

Large ions are Destabilised/Polarised/Distorted by cations

Carbonates/Nitrates

A

They’re broken down by negative ions

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17
Q

Thermal Stability

Trend 1)

A

Greather distortion = more unstable the compound

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18
Q

Thermal Stability

Trend 2)

A

Larger cations = smaller distortion than small cations
lower charge density

-down G2 atomic radius increases
↳ electrons = further away & ion can’t hold onto them
↳ if it can’t even do this, then it can’t pull another’s electrons

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19
Q

Charge Density

Charge per space/ Charge over smaller space

A

Larger cation = lower CD
↳ less distortion = more stable the nitrate/carbonate compound

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20
Q

Top G2 = most polarising

Smaller atomic radius = more polarising
Higher charge = more polarising

A

G2 cations have a 2+ charge compared to a +1 from G1 so G2 carbonates/nitrates = less stable than G1

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21
Q

Anions

Thermal Stability Testing

Nitrate Decomposition

A
  • Test to see how long it takes for a certain amount of O2 to be released

Glowing splint relights if positive

  • Test to see how long it takes for NO2 to form

NO2 gas is brown

22
Q

Anion

Thermal Stability Testing

Carbonate Decomposition

A
  • Test to see how long it takes for a certain amount of CO2 t be released

Limewater goes cloudy if positive

23
Q

Cation

Flame Test

Equipment

A
  • HCl
  • Metal solutions (cations)
  • Nichrome wire
  • Bunsen Burner
24
Q

Cation

Flame Test

Practical done because some metals have the same colour

A
  1. Take nichrome wire & dip into HCl
  2. Put that wire into flame
    ↳ step 1 & 2 cleans loop
  3. Dip wire into one of the metal solutions
  4. Place that wire into the flame at 45° just below top of the flame for 5 secs
  5. Observe colour & note it down
  6. Repeat 1-8 until you’re done w all solutions
  7. Repeat procedure again for each solution
    ↳ some reactions occur quickly : recheck colour

!!If all tests are orange, your test is contaminated!!

25
Colours of metal ions
***G1*** * Li+ = red * Na+ = yellow/orange * K+ = lilac * Rb+ = red **G2** * Ca2+ = red * Sr2+ = crimson red * Ba2+ = green **neither** * Cu2+ = blue/green
26
Down G7 = **less reactive** | As they're reduced, they oxidise another substance (oxiding agents)
* Larger G7 atoms are less reactive **:** reactivity decreases down the group (electronegativity) ↳ due to increase in QL
27
Down G7 = **Mp/Bp increase**
**Mp** Down G7, states change ↳ more energy is needed to break bonds **Bp** Down G7, there are more QL **:** more electrons ↳ more London Forces ↳ more energy needed to break these
28
Group 7 Properties Table
29
G7 Properties by theirselves
* Diatomic * Non-polar ↳ can't form ions **:** they can't carry a charge **:** can't conduct electricity or dissolve in water ↳ but can dissolve in organic compounds i.e. **HEXANE**
30
G7 Colours
31
Halide
Charged halogen
32
Displacement
Where an element replaces another in a compound
33
Halogens can displace halide ions from solutions
The more reactive the halogen, the more able it is to displace a less reactive halide ↳ they have a higher oxidation strength * The colour expressed within the solution = the colour of the uncombined halide
34
Halogens can react w G1 & G2 metals
35
Disproportionation w Cold Alkali | Sodium Hydroxide
g + aq → aq + aq + l
36
Disproportionation w Cold Alkali Example | Chlorine & Sodium Hydoxide
* Make bleach ↳ bleach is used in water treatment & textiles
37
Disproportionation w Hot Alkalis
g + aq → aq + aq + l
38
**HALIDES** lose electrons if there's less of a pull from nucleus & outer electron is weak
39
Down G7 = **attraction weaker**
* Atomic radius increases **:** electrons are further away ↳ there's more shielding from inner electrons
40
All halides react w CONCENTRATED sulfuric acid to give a hydrogen halide
Concentrated Sulfuric Acid = always liquid
41
Reaction of KF/KCl w H2SO4
* Oxidation number for Sulfur doesn't change ↳ F- & Cl- ions aren't strong enough reducing agents to reduce Sulfur's oxidation number * This reaction isnt redox as the oxidation number of the halide & sulfur remain the same * Produce misty fumes
42
Reaction of KBr w H2SO4
* 2nd reaction occurs instantly after 1st * HBr dissolves in the solution bc it isn't isolated * HBr produces mistry fumes Br gives its electron more easily to S & drops S down to ox. no° 4 ↳Br is a stronger reducing agent than Cl- & F- bc it has more electrons ↳ this is redox reaction as ox. no° change
43
Reaction of KI w H2SO4
* 3 reactions 1. 1st reaction occurs 2. 2nd reaction occurs instantly after 3. 1st reaction isn't stopped **:** reoccurs 4. 3rd reaction produced slightly after
44
Summary | Strength of reducing agents increases → causing S ox. number to decrease
**Flourine/Chloride** +6 → +6 **Bromide** +6 → +4 **Iodide** +6 → +4 -2
45
Test for Halides
* Add nitric acid ↳ removes interface ions * Add silver nitrate solution * A precipitate of a silver halide will form
46
Precipitate colour based on Halide | Precipitate- solid that doesn't dissolve in a liquid
Flourine = none formed Chloride = white Bromide = cream Iodide = yellow
47
To confirm test for Halides
* Add ammonia (NH3) ↳ it is sometimes difficult to see precipitate based on te halide test ↳ ammonia allows verification **Dilute Ammonia** * Only breaks down the precipitate in AgCl into a solution * Unaffects AgBr & AgI **Concentrated Ammonia** * Only breaks down precipitate in AgBr into a solution * Unaffacts AgI AgI is unaffected by both types of ammonia
48
Polyatomic Ions | Carbonates (CO2)
* If heated or HCl is added it breaks the solution down * CO2 is given off ↳ collect it & put into limewater Positive Test: turns cloudy
49
Polyatomic Ions | Sulfate (SO4 2-)
* Use HCl ↳ removes contaminates * Followed by BaCl ↳ produces BaSO4 (contains sulfur) Positive Test: white precipitate present
50
Ammonium Compounds | (NH4 +)
* NH3 can be detected using damp red litmus paper ↳ turns blue * For NH4+ add NaOH & heat gently ↳ gives off NH3 gas (litmus paper test + smells) If NH3 is involved, NH4 ions are present in sample