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Chemistry > Group 2 & Group 7 > Flashcards

Group 2 & Group 7 Flashcards

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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
Q

Colours of metal ions

A

G1
* Li+ = red
* Na+ = yellow/orange
* K+ = lilac
* Rb+ = red

G2
* Ca2+ = red
* Sr2+ = crimson red
* Ba2+ = green

neither
* Cu2+ = blue/green

26
Q

Down G7 = less reactive

As they’re reduced, they oxidise another substance (oxiding agents)

A
  • Larger G7 atoms are less reactive : reactivity decreases down the group (electronegativity)
    ↳ due to increase in QL
27
Q

Down G7 = Mp/Bp increase

A

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
Q

Group 7 Properties Table

A
29
Q

G7 Properties by theirselves

A
  • 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
Q

G7 Colours

A
31
Q

Halide

A

Charged halogen

32
Q

Displacement

A

Where an element replaces another in a compound

33
Q

Halogens can displace halide ions from solutions

A

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
Q

Halogens can react w G1 & G2 metals

A
35
Q

Disproportionation w Cold Alkali

Sodium Hydroxide

A

g + aq → aq + aq + l

36
Q

Disproportionation w Cold Alkali Example

Chlorine & Sodium Hydoxide

A
  • Make bleach
    ↳ bleach is used in water treatment & textiles
37
Q

Disproportionation w Hot Alkalis

A

g + aq → aq + aq + l

38
Q

HALIDES lose electrons if there’s less of a pull from nucleus & outer electron is weak

A
39
Q

Down G7 = attraction weaker

A
  • Atomic radius increases : electrons are further away
    ↳ there’s more shielding from inner electrons
40
Q

All halides react w CONCENTRATED sulfuric acid to give a hydrogen halide

A

Concentrated Sulfuric Acid = always liquid

41
Q

Reaction of KF/KCl w H2SO4

A
  • 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
Q

Reaction of KBr w H2SO4

A
  • 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
Q

Reaction of KI w H2SO4

A
  • 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
Q

Summary

Strength of reducing agents increases → causing S ox. number to decrease

A

Flourine/Chloride
+6 → +6
Bromide
+6 → +4
Iodide
+6 → +4 -2

45
Q

Test for Halides

A
  • Add nitric acid
    ↳ removes interface ions
  • Add silver nitrate solution
  • A precipitate of a silver halide will form
46
Q

Precipitate colour based on Halide

Precipitate- solid that doesn’t dissolve in a liquid

A

Flourine = none formed
Chloride = white
Bromide = cream
Iodide = yellow

47
Q

To confirm test for Halides

A
  • 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
Q

Polyatomic Ions

Carbonates (CO2)

A
  • 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
Q

Polyatomic Ions

Sulfate (SO4 2-)

A
  • Use HCl
    ↳ removes contaminates
  • Followed by BaCl
    ↳ produces BaSO4 (contains sulfur)

Positive Test: white precipitate present

50
Q

Ammonium Compounds

(NH4 +)

A
  • 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

Chemistry (13 decks)

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