REFLECTION ON GROUP 2 AND 17 REVISION by Pooganeswari Siteram Pillai

Jasmine

2021-08-18 01:31:38 UTC

Revised on ( group 2 ) :
- MP and BP decreases down the group ( increase in atomic radius )
- reactivity increases down the group ( easier to lose electrons )
- increases in hydroxide solubility down the group
- decreases in carbonate solubility down the group
- increases in thermal stability down the group
- electronegativity decreases down the group

Revised on ( group 17 ) :
- colors get darker down the group
- increased MP and BP down the group due to VDW
- decreased volatility down the group as MP and BP increases
- less reactive down the group as bond length increases, and bond energy decreases
- less electronegative down the group due to increase in number of shells
- Cl -> white ppt
- Br -> cream ppt
- I -> yellow ppt

I need to revise more on the trends and reactions of both group 2 and group 17

Jacksen JC2T

2021-08-18 01:33:58 UTC

Today I revised about
- trend of group 2 and 7 metals
> mp/bp , volatility,
>reactivity
>solubility of hydroxide and sulfate, PH
>Electronegativity, IE
> color and solubility of group 7 ions in ammonia
>I need to revise more on reactions of metal with water/steam/oxygen and acid

Thomson JC2T

2021-08-18 02:42:50 UTC

For group 2 metals i revised on the properties down the group

melting and boiling point, solubility of sulphates, electronegativity and solubility of carbonates decreases down the group.

thermal stability, reactivity and solubility of hydroxide increases down the group.

For group 17 i revised on reactions and properties

reaction of sodium halides and sulfuric acid, disproportionation and testing

the properties revised are, melting and boiling point, colour, volatility, electronegativity and hydrogen halide stability

Catherine JC2T

2021-08-18 02:58:57 UTC

What I learnt:

Group 2

melting point decrease (radius increase, weaker attraction)
reactivity increase (shell increase, lose electrons easier)
acts as a good reducing agent
solubility of hydroxides increase, solubility of sulfates decrease

Group 17

mp/bp increases so volatility decrease
reactivity decrease/ electronegativity decreases (shielding effect)
halogens dissolve in cyclohexane (can see colors)
thermal stability decrease (bond energy decrease)
test for halide ions
cannot use conc. H2SO4 for preparing HBr and HI as they have low bond energy, so they easily decompose.

What I should revise more on:

metal carbonate reactions
products from preparation of hydrogen halide
disproportionate reaction of Cl2 in cold and hot alkali

Davis JC2Grace

2021-08-18 06:41:46 UTC

Group 2
*Down the Group*
- Metals get more reactive
- Hydroxides becomes more soluble
- Sulfate becomes less soluble
( Carbonates dows not react with water)
- Higher temperature for thermal decomposition to occur

- Carbonates with dilute acids
- reacts with sulfuric acid and nitric acid
- Note: All nitric salts formed are soluble in water

- Uses : Slaked lime to increase pH of soil
Calcium hydroxide neutralise acids, raising pH

Group 17 ( Halogens)
*Down the group*
- Gets less reactive
- Less thermally stable
- Lower bond energy

Note: AgCl : White ,AgBr: Cream , AgI: Pale Yellow

Displacement reaction
: more reactive halogen displaces a less reactive halogen from a halide solution of the less reactive halogen

When reacted with cyclohexane (forms layer):
Iodine : Purple
Bromine : Orange
Chlorine : Pale green

Lastly, I learnt the reaction of Halide Ions

I need to revise more on:
- Memorising the trends
- The products of oxidation of HBr and HI

Bendict JC2Truth

2021-08-18 06:57:59 UTC

Today i revised one the group 2 metals and the group 17 halogens.

Group 2
- Boiling point decreases down the group
- solubility of sulfates decrease down the group
- Reactivity increases down the group

Group 17
- melting and boiling points increase down the group
- Volatility decreases down the group
This is because, going down the group, the vdw forces increase making it harder to seperate the bonds.
- Reactivity decreases down the group
- Thermal stability decreases down the group
- Electronegativity decreases down the group

I need to revise more on the conditions, equations and test reactions on the group 2 metals.

Christopher JC2T

2021-08-18 06:59:20 UTC

Today we learnt about the trends of the physical and chemical properties of group 2 and 17 elements. This includes their reactivity, m.p. and b.p., the different reactions with various substances, and the reasons behind the trend.

Michael jc2t

2021-08-18 07:03:32 UTC

Group 2: Hydroxides become more soluble and PH increase down the group while group 2 sulfates become less soluble down the group. Group 2 carbonate is insoluble in water. The temperature needed for thermal decomposition down group 2 increases. Melting point decrease down group 2. Reactivity increases down group 2.

Group 17: Down the group will be less thermally stable. A more reactive halogen can displace a less reactive halogen. Iodine will turn into a purple layer when reacted with cyclohexane. Chlorine will be green and bromine will be brown.

Ryan JC2Truth

ryanant2004 — 2021-08-18 07:11:23 UTC

Group 2:
I learned that boiling point and melting point decreases down the group, as the atomic radii increases. The solubility of hydroxides and the thermal stability increases down the group, while the solubility of carbonates decreases. The reactivity increases down the group.

Group 17:
The melting point and boiling point increases down the group, while both the volatility and the reactivity decreases down the group. The thermal stability and the electronegativity decreases down the group.

I need to revise more on the trends of group 2 metals including the equations and the reactions.

Audrey JC2T

2021-08-18 07:14:38 UTC

Group 2 (down the group) :
- mp and bp decreases (increased shielding, decreased charge density)
- electronegativity decreases
- reactivity increases
- solubility of OH increases
- solubility of sulfate decreases
- thermal stability of carbonate increases
- thermal stability of nitrate increases
- pH increases
- reaction with H2O more vigorous
- group 2 nitrates thermal decomposition to form metal oxide, NO2 and O2

Group 17 (down the group)
- colour becomes darker
- reactivity decreases
- volatility decreases
- thermal stability of halide decreases
- mp bp increases (VDW increases)
- silver halide colour : Cl (white), Br (cream), I (yellow)
- colour with cyclohexane : Cl (green), Br (orange), I (purple)
- more reactive halogen decomposes less reactive halogen
- HBr and HI cannot be prepared in situ with conc. H2SO4

I should revise more on :
- Disproportionate reaction of Cl with NaOH
- Memorising trends

Josh JC2Truth

2021-08-18 08:51:55 UTC

Today we revised about the trends of group 2 and group 17. Some points are like mp and bp, reactivity and more. The cause of these trends as well.

I need to revise more on the reactions with the group 2 metals and group 17 halogens with other substances. I also need to freshen up on the disproportionation reaction.

sharon jc2t

2021-08-18 10:34:29 UTC

group 2 (down the group)

— ionisation energy increases

— reactivity increases

— electronegativity decreases

— melting point generally decrease but an increase from Mg to Ca

— density decreases

— solubility of metal sulfates decreases down the group while hydroxides increases down the group

— no reaction of group 2 carbonates with water

— group 2 carbonates + acid to form salt, water, and carbon dioxide

group 17 (down the group)

— colour of halogens darker

— melting and boiling point increases

— volatility decreases

— reactivity decreases

— electronegativity decreases

— thermal stability decreases

— cyclohexane is used when there is difficulty in seeing the observation. iodine(purple), bromine(orange), chlorine(pale green)

— displacement reaction : more reactive halogen can replace a less reactive halogen

— fluorine react explosively in cool and dark conditions

— chlorine react explosively in sunlight

— testing for halide ions (AgCl white, AgBr cream, AgI yellow) —further testing — (conc. and dilute ammonia)

— reactions of halide ions with concentrated sulfuric acid

— easier to oxidise hydrogen halides

— disproportionation reaction (cold - NaClO) and (hot - NaClO3)

study more on
- the reactions of halide ions with concentrated sulfuric acid
- and its products

Frederic JC2Truth

2021-08-18 11:47:44 UTC

Today we revised about group 12 and 17 trends such as MP, BP, density, reactivity, electronegativity, volatility, solubility of hydroxides and sulfates colour of halogens going down the group, test for halides with ammonia and thermal stability down the groups.
I was reminded that disproportionation reaction have different results when the temperature of the alkali varies, cold alkali will form NaCIO while hot alkali will form NaCl3O.
We also revised about the test for halides which halide ions can be tested using Silver Nitrate solution. The test solution is made using a few drops of dilute nitric acid, followed by a few drops of silver nitrate solution. Different colored solutions can be formed.

Dylan JC2G

2021-08-18 12:38:33 UTC

GROUP 2-
> Going down the group:
- MP and BP decreases as metallic radius increases, so greater distance between nucleus and sea of delocalised electrons
- Reactivity increases, as the size of the cation increases, weaker attraction between and valence electrons, so it is easier to lose electrons
- Electronegativity decreases
- Ionization energy decreases, as the size of the atom increases, there are weak attractive forces between nucleus and valence electrons
- Density (Be to Ca decrease, as an increase in mass is lower than the increase in volume and for Ca to Ba, it's the opposite)
- Reducing Power increases (all Group 2 are reducing agents)

> Thermal Decomposition
- Thermal stability of Group 2 Carbonates & Nitrates increases

> Solubility
- Increases in hydroxide solubility
- Decreases in carbonate solubility

> Flame Tests
- Ca -> Brick Red
- Sr -> Scarlet Red
- Ba -> Apple Green

> Reaction with oxygen
> Reaction with water
> Group 2 Carbonates
> Use of Group 2 Compounds

GROUP 17: HALOGENOALKANES-
> Going down the group:
- Colour gets darker
- MP and BP increases due to the increasing VDW forces
- Volatility decreases as MP and BP increases
- Reactivity decreases as there is a greater number of shells, so atomic radius increases, and hence it's more difficult to attract electrons to form a full outer shell
- Less electronegative as an increase in the number of shells, so radius increases, hence more difficult to attract bonding pair of electrons
- Thermostability of Hydrogen Halides decrease as atomic radius increases, bond length increases, hence bond is easier to break

> Displacement Reactions
> Reaction with Hydrogen
> Reaction of Halide ions with conc. Sulfuric acid
> Disproportionation reaction

> Testing for halide ions:
Solution + HNO3 + AgNO3
- Cl2 -> white ppt
- Br2 -> cream ppt
- I2 -> yellow ppt
For further testing, add dilute ammonia then concentrated ammonia,
- AgCl will dissolve in dilute ammonia
- AgBr will dissolve in concentrated ammonia
- AgI does not dissolve

What to revise on:
> I feel like I need to revise more on the different kinds of trends and reactions for both groups as sometimes I mixed both of them up, so I will try to read through notes or watch Mr Gopi's video to ensure I remember everything before the exam.

Angela JC2G

2021-08-18 12:41:36 UTC

GROUP 2
- MP & BP decreases down the group because ionic radius increases
- Reactivity increases down the group, as shells increase and it would be easier to lose electrons
- Solubility of sulfates and carbonates decreases down the group
- Solubility of hydroxides increases down the group
- Thermal stability of nitrates and carbonates increases down the group
- Electronegativity decreases down the group
- pH increases down the group

GROUP 17
- Colors get darker down the group
- MP & BP increases down the group (more VDW)
- Volatility decreases down the group
- Reactivity decreases down the group (bond length increases, bond energy decreases)
- Thermal stability decreases
- Electronegativity decreases down the group
- AgCl = white ppt
- AgBr = cream ppt
- AgI = yellow ppt

In cyclohexane
- Cl = green
- Br = orange
- I = purple

Effect on precipitate of adding ammonia solution
- Cl = dissolves in both dilute and concentrated ammonia solution
- Br = dissolves only in concentrated ammonia solution
- I = does not dissolve

Disproportionation reaction
- Cold = NaClO
- Hot = NaClO3

I need to revise more on the trends, disproportionation reaction, reaction of halide ions with concentrated H2SO4

MichelleV Jc2Truth

2021-08-18 12:58:48 UTC

Group2: Down the group,
- increased distance between electrons so MP decrease
- metallic bonding weaker as there are more shells
- more reactive
- hydroxides more soluble
- sulfates less soluble
- group 2 flame test (calcium : brick-red, strontium : scarlet/red, barium : apple-green)
- group 2 good as reducing agents
- basic oxide with oxygen
- group 2 with water

Group 17: Down the group,
- MP/BP increases
- volatility increases
- reactivity decrease because of shielding effect
- dissolve in cyclohexane (Cl : green, Br: Orange, I : purple)
- thermal stability increase because bond energy decreases down the group
- can be used to test for halide ions (Cl2 : white precipitate, Br2 : cream precipitate, I2 : yellow precipitate)
- adding ammonia to precipitate effects (Cl : dissolves in dilute and conc. ammonia, Br : dissolves ONLY in conc. ammonia, I : does not dissolve)
- displacement reaction
- disproportionation reaction (Cold : NaClO, Hot: NaClO3)

What i need to revise on:
- memorising the colors of the cyclohexane reaction
- the trends
- different precipitates for testing for halides
- group 2 flame test
- disproportionate reaction of Cl2 in hot or cold alkali

Keira JC2G

2021-08-18 13:21:36 UTC

Today we revised that down the group of group 2,
- MP & BP decreases
- reactivity increases
- electronegativity decreases
- ionisation energy decreases
- thermal stability increases
- solubility of sulfates and carbonates decreases
- solubility of hydroxides increases

down group 17,
- colour gets darker
- MP & BP increases
- reactivity decreases
- volatility decreases
- electronegativity decreases
- hydrogen halides have decreasing thermal stability

Halide ions can be tested with silver ions: AgCl - white, AgBr - cream, AgI - pale yellow

sodium gives a yellow colour using flame test

when iodine is dissolved in cyclohexane, it gives a purple colour, bromine gives an orange colour and chlorine gives a pale green colour

I need to revise the reactions of halide ions with concentrated H2SO4, memorise the trends of each group and the disproportionation reactions.

Josh JC2G

2021-08-18 13:34:32 UTC

> things I need to revise on :
- the reactions of
NaCl and H2SO4
NaBr and H2SO4
And the most annoying and confusing one , :
NaI and H2SO4

And oh also the disproportionation reactions of Chlorine and hot/cold alkali

Ashley JC2Grace

2021-08-18 13:44:59 UTC

Today, we revised Group 2 and 17. I need to revise Group 2 reactions with steam and water ( and how to differentiate which with Hydrogen and not ), insolubility of Group 2 carbonates and other Group 2 salts.

For Group 17, I need to revise the conditions needed for solubility tests of hydrogen halides and conditions to form hydrogen halides to show reactivity. I also need to memorise that redox reactions of NaBr and NaI with H2SO4.

I also need to memorise the disproportionate reactions of CL2 with NaCL hot and cold.

Geoffrey jC2 Truth

2021-08-18 14:00:32 UTC

Today we learnt about the trends of the physical and chemical properties of group 2 and 17 elements. their trends and reactions.

Need to revise more on their reactions and memorize the chemical equations and trends

Yeewen JC2Truth

yeewenpoh — 2021-08-18 14:12:05 UTC

Revision on Group 2 elements

- Boiling point n melting point decreases down the group (Sudden drops in Mg)
- Reacts with excess oxygen to form white solid oxides
- Group 2 hydroxides increases in solubility down the group
- Group 2 sulfates decreases down the group
Flame test
- Calcium; brick red

- Strontium; scarlet red

- Barium; apple green

Revision on Group 17 elements
- Boiling point n melting point generally increases down the group
- Thermal stability decreases down the group
- Reactivity also decreases down the group
- Colour becomes darker down the group (starting with yellow)
- In a displacement reaction, halogen is replaced with another halogen with higher reactivity.

I need to make sure i can remember the colours and observations in the tests

Wilson

2021-08-18 15:05:02 UTC

We revised on Group 2 and 17s.
For group 2 metals, the solubility of hydroxides increases down the group while the trend is opposite when it comes to group 2 metal sulfates. Down the group, the melting point and boiling point, electronegativity and ionization energy decreases. However, the reactivity and reducing power increases. There are also some reactions that group 2 metals and its compounds undergo, such as with oxygen and water.
Moving on, we also learnt about Group 17 Halogens. Its color gets darker down the group and its melting and boiling point increases. However down the group, it becomes less reactive. The halides down the group decrease in thermal stability. However, the melting point and boiling point increases down the group. There are also reactions that these halogens undergo.

Ella Suita JC2 Grace

2021-08-18 15:31:09 UTC

GROUP 2

(Trend down the group)
1. Ionisation Energy decreases

Refer to radii, nuclear attractive force, ease of removing electron.
2. Reactivity increases

Refer to radii, nuclear attractive force, ease of losing electron to form ions.
3. Electronegativity decreases

Refer to radii, charge, charge density, ability to attract bonded pair of electrons.
4. Melting Point decreases

Refer to metallic bonding strength, distance between metal cation and delocalised electrons.
5. Density decreases to Ca then increases

Refer to increase in volume and mass and which factor outweighs which.
6. Hydroxide solubility increases
7. Sulfate solubility decreases

GROUP 17

(Trend down the group)
1. Colour gets darker
2. MP and BP increase

Refer to increase in e- number and VDW strength.
3. Volatility decreases
4. Reactivity decreases

Refer to shielding and ability to gain electron.
5. Electronegativity decreases

Refer to radii, distance, force of attraction.
6. Displacement occurs when a less reactive element is replaced by a more reactive one.
7. Reaction with H2

F2: explosive in cool and dark

Cl2: explosive in sunlight

Br2: slowly when heated

I2: forms equilibrium when heated
8. Thermal stability of HX decreases

Refer to bond length and strength.

Jennifer JC2G

2021-08-18 18:39:08 UTC

Group 2
- Ionization energy decreases
- Reactivity decreases
- Electronegativity decreases
- Melting point increases
- Density decreases
- Hydroxides get more soluble
- Sulfates get less soluble
- Carbonates cannot react with water
- Carbonates can react with dilute acid to form a Salt, Carbon dioxide & Water
- Magnesium carbonate is the only one in Group 2 that would react with excess sulfuric acid. But it only reacts slightly

Group 17
- Color gets darker
- Melting point increases
- Boiling point increases
- Gets less volatile
- Reactivity decreases
- Electronegativity decreases
- Can do displacement reaction as long as the halogen trying to displace is more reactive
- Thermal stability decreases

Colors
- AgCl : White ppt
- AgBr : Cream
- AgI : Yellow

- Cl : Green
- Br : Orange
- I : Purple

Learn more
- Which ones are which

Cleantha JC2G

2021-08-18 18:50:21 UTC

Group 2:

Ionization energy decrease down the group as atomic radii increases so attractive force between nucleus and valence electrons decreases
Reactivity increases
Electronegativity decreases as atomic radii increases but charge remains constant
Melting point decreases as metallic bond becomes weaker
Density decreases from Be to Ca but increases from Ca to Ba
There is not reaction of group 2 metal carbonate with water

Group 7:

Colour gets darker as you go down the group
Melting and boiling point increases as VDW becomes greater
Volatility decrease
Reactivity decreases as the number if shells increases and gaining electron is harder
Electronegativity decreases

Earlene JC2G

2021-08-19 02:55:26 UTC

Group 2

1. Down the group, the increase in distance and shielding effect outweighs the increase in nuclear charge. This contributes to the decreasing ionisation energy down the group and increasing reactivity down the group.

2. Magnesium has a special lattice structure which explains its melting point.

3. Hydroxides become increasingly soluble down the group.

4. Sulfates become decreasingly soluble down the group.

5. The reaction with sulfuric acid will be less vigorous going down the group, observation would be less effervescence down the group and formation of an insoluble precipitate.

Group 17

1. Melting and boiling point increases down the group due to increase in vdw forces.

2. Reactivity and electronegativity decreases down the group due to the increase in atomic radii.

3. Cyclopropane colours: iodine - purple, chlorine - pale green, bromine - orange

4. Thermal stability of hydrogen halides decrease down the group due to the increase in bond length.

5. Reaction with concentrated sulfuric acid is not ideal to produce HBr and HI as they are easily oxidised afterwards by the concentrated sulfuric acid which causes a mixture of products to be produced.

6. Disproportionation reaction: chlorine is both oxidised and reduced ; in cold alkali NaCl, NaClO, and H2O is produced ; in hot alkali NaCl, NaClO3 and H2O is produced.

What I need to revise

1. Reaction of group 2 metals with oxygen and water

2. Flame tests

3. Thermal decomposition of group 2 nitrates and carbonates

4. Uses of group 2 compounds

5. Reaction of sodium halides with concentrated sulfuric acid

6. Disproportionation reaction

michelle jc 2 grace

2021-08-19 03:49:14 UTC

what i learnt:

colour of halogens get darker down the group as they have low ionization energy
melting and boiling point of halogens increases down the group because the size of molecule increases due to the addition of the number of shells
volatility decreases going down the group as melting points increases making it hard to exist as a gas under normal conditions
reactivity decreases as it goes down the group because the outer shell is further away from the nucleus
electronegativity decreases as the outer shell will be further away from the nucleus so it will be harder to pull other electrons towards itself
going down the group hydrogen halides become less thermally stable as the bond strength of the molecules decreases due to the larger bond length
the group 2 metals burn in air and form white solid oxides
berrylium does not react with cold water but it reacts with steam at 700 degrees or more to produce white berrylium oxide and water
magnesium reacts with steam to form magnesium hydroxide and hydrogen gas
calcium strontium barium and radium reacts more readily with cold water as it goes down the group to form white metal hydroxides and hydrogen gas

what i need to revise

reactions
remember colours and observations
flame tests
remember equations
trends

Lindsay JC2G

2021-08-19 13:19:10 UTC

Group 2
> reactivity increases down the group
> alkaline earth metals
> flame tests
- calcium compounds - brick red
- strontium compounds - scarlet red
- barium compounds - apple green
> reaction with water
- Mg(s) + 2H2O(l) -> Mg(OH)2(aq) + H2(g)
(very slow reaction)
- Ca(s) + 2H2O(l) -> Ca(OH)2(aq) + H2(g)
(reacts more steadily than Mg)
- Mg(s) + H2O(g) -> MgO(s) + H2(g)
(vigorous)
> hydroxides becomes more soluble down the group
> sulfates becomes more insoluble down the group
> carbonates are insoluble in water
> reacts with dilute acids to produce salt, water and carbon dioxide
> thermal decomposition
- temperature at which it takes place decreases down the group
- MgCO3(s) -> MgO(s) + CO2(g)
- 2Ca(NO3)2(s) -> 2CaO(s) + 4NO2(g) + O2(g)

Group 17
> gets less reactive down the group
> becomes darker down the group
> more reactive halogen can displace less reactive
> gets less thermally stable down the group

Elizabeth Donna

2021-08-20 00:43:35 UTC

Group 2 & Group 17

GROUP 2
- Alkaline earth metals
- Get more reactive going down the group
* Ba easily react
* 2e- -> tendancy to lose electron
- MP : Generally downward trend ,excpet Mg (Be-Mg : Drop)
*Metallic radius increase , strength from cations and delocalise electron weaker
*Mg : metallic radius (bigger) , metallic bonding weaker - the way they are arrange differently so metallic strength decreasing
- Density :
*Be-Ca : decrease, the volume is greater than mass
*Ca- Ba: Increase, Increase in mass is greater than increase in volume

- Mg
Reaction with O2
* Product : MgO
* Bright white flame
MgO + Reaction with H2O
* Product : Mg(OH)2 alkaline/ basic oxide

- Group 2 :
1. OH-, hydroxides : Going down the group , more alkaline , so more soluble , ph increase
2. SO4- , Sulfate : less soluble going down the group

Flame test :
- Calcium : Brick red
- Strontium : Red / scarlet
- Barium : apple-green

Reaction with water
- Mg : (l)
* Very slow with cold water
* Product : Mg(OH)2 (aq) + H2
- Mg : (g)
* Vigorously
* Product : MgO(s) + H2
- Ca : (l)
* React more readily than Mg
- Reactivity with water increase going down the group

(Strontium no reaction with water)

IE :
- Going down the group decrease
- Across increase

Group 2 Carbonates with water
- No reaction / insoluble in water

Group 2 Carbonates with dil H2SO4
- insoluble
- Product : salt + H2O (l)

Group 2 Carbonates with dil HNO3
- Product : salt + H2O + CO2
- soluble

Group 2 oxide don't react with water

Thermal decomposition increase going down group 2

Uses of group 2 compounds
- Ca(OH)2 - basic : Slaked Lime
* Raise pH of acidic soil
* Add water -> turn lime water - test for co2
- CaO : quick lime

GROUP 17
- Halogens : Going down the group
* less reactive
* Darker colour
* Electronegativity : ability to pull covalently bonded electrons
1. less electronegativity
Radius increase , further away , more shielding effect
- Displacement reaction
* F, Cl, Br , I - more reactive halogens can replace less reactive halogens from a halide solution
* Cyclohexane : Test
Water : form a top layer
I2 : Purple
Br2 : Orange
Cl2 : Pale green

Reaction with Hydrogen
- Going down the group : less reactive
* Ability to attract electron is less
- Hydrogen halides get less thermally stable down the group
* HF (most Thermally stable) - HI (least thermally stable)
* HF (short bond length -> Harder to break the bond) - HI (longer bond length -> easier to break the bond)

Testing for halide ions :
- Cl- : White (AgCl)
- Br- : Cream (AgBr)
- I- : Pale yellow (AgI)
- Add dil ammonia / conc. ammonia

Halide ions + conc. Sulfuric acid
- conc. H2SO4 - Strong oxi agent
- HBr : continue to react H2SO4 and give other products
- NaI :
* Sulfur : Yellow solid
* Hydrogen sulfide : strong smell of bad eggs
* Iodine : Purple / violet vapour

Disproportionation reaction (memorize)
- Same element get both oxi and reduce
- Memorize eq. :
*Cl (in cold alkali) 15 degree c
*Cl (in hot alkali) 70 degree c

*OIL RIG

Need more practice :
1. 🤬 eq.
2. 🤬 reactions