What is the trend in electronegativity down the group
Decreases
Atomic radius increases
shielding increases
attraction between nucleus and electrons decreases
What is the trend in boiling point down the group
Increases
larger molecules more electrons
stronger london dispersion forces
require more energy to overcome
What is the trend in oxidizing ability of the halogens down the group
Decreases down the group
Chlorine is the strongest oxidizing agent because it more readily accepts electrons
Why does oxidising ability decrease down Group 7?
Atomic radius increases
Shielding increases
Weaker attraction for an incoming electron
Less easily reduced → weaker oxidising agent.
What is observed in displacement reactions of halogens with halide ions
A more reactive halogen displaces a less reactive halide
What is the trend in reducing ability of halide ions down the group
Reducing ability increases down the group Chlorine
Because larger the ion, easier it to loose an electron
What happens when NaCl reacts with conc sulfuric acid
Steamy fumes of HCL
no more reaction (Cl is poor reducing agent)
acid base reaction
What happens when NaBr reacts with conc sulfuric acid
Steamy fumes of HBr
Orange vapor of Br2
Br- reduces H2S04 to S02-
acid base and redox
What happens when NaI reacts with conc sulfuric acid
Steamy fumes of HI
purple vapor of I2
Yellow solid sulfur
Bad smell of H2S
redox reaction
What is used to test halide ions
Acidified silver nitrate solution
Why is the silver nitrate acidified with nitric acid?
To remove carbonate ions.
Carbonates would form Ag₂CO₃ precipitate → false positive.
Nitric acid is used because nitrate ions do not form a precipitate with Ag⁺.
Why is silver nitrate acidified
To remove carbonate or hydroxide ions that could give false results
What are the colors of silver halid ppts
AgCl : white
AgBr : cream
AgI : yellow
why is ammonia added, How does solubility in ammonia distinguish the halides
to distinguish between silver halides
AgCl : dissolves in dilute NH3
AgBr: dissolves only in conc NH3
AgI: doesn’t dissolve in NH3
What is the trend in solubility of silver halides in ammonia?
Solubility decreases down the group.
AgCl dissolves in dilute NH₃
AgBr dissolves in concentrated NH₃
AgI does not dissolve
What happens when chlorine reacts with water
Cl2 +H2O –> HCl + HClO or
Cl2+H2O⇌Cl−+ClO−+2H+(chlorate ions)
disproportionation reaction
What happens when chlorine reacts with water in sunlight
2Cl2 +2H2O -> 4HCl +O2
Why is chlorine used in water treatment despite being toxic
Kills pathogens
What is formed when chlorine reacts with cold, dilute aqueous NaOH
NaCl+ NaClO+H2O (sodium chlorate used as bleach)
What is observed in displacement reactions?
Cl₂ displaces Br⁻ and I⁻
Br₂ displaces I⁻
I₂ displaces none
Cl +KBr - bromine is formed so is brown
(Cl₂ + KI) -Solution turns brown (iodine formed).
(Br₂ + KI) - Solution turns brown (iodine formed).
Br₂ + KCl → no reaction
I₂ + KCl → no reaction
Why does reducing ability increase down Group 7?
Ionic radius increases
Outer electrons further from nucleus
Easier to lose electron
Why is chlorine added to water?
Kills bacteria
Prevents disease
Benefits outweigh toxic risks
what is the reducing ability down the group
increases
