Group 7: The Halogens

• In which group of the periodic table are halogens found?

  Group 7
• How many electrons do halogens have in their outermost shell?

  Seven electrons
• What type of elements are halogens?

  Highly reactive non-metals
• What state do halogens exist in at room temperature?

  Diatomic molecules
• What happens to the boiling point of halogens as you move down Group 7?

  The boiling point increases
• What type of forces exist between halogen molecules?

  Van der Waals forces
• How do larger halogen atoms affect van der Waals forces?

  They lead to stronger van der Waals forces
• What trend occurs in electronegativity as you move down Group 7?

  Electronegativity decreases
• What is electronegativity?

  The tendency to attract bonding electrons
• How does atomic radius affect effective nuclear charge?

  Effective nuclear charge decreases with increasing radius
• What is the state and color of fluorine (F₂) at room temperature?


  Pale yellow gas
• What is the electron configuration of chlorine (Cl₂)?

  1s² 2s² 2p⁶ 3s² 3p⁵
• What is the state and color of bromine (Br₂) at room temperature?

  Reddish-brown liquid
• What is the electron configuration of iodine (I₂)?

  1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁵
• What are the characteristics of displacement reactions involving halogens?

  • More reactive halogen displaces less reactive halogen
  • General formula: X₂ + 2MY → 2MX + Y₂
• What happens when chlorine water is added to potassium bromide (KBr)?


  Chlorine displaces bromide ions
• What is formed when chlorine displaces bromide ions from KBr?

  Potassium chloride (KCl) and bromine (Br₂)
• What is disproportionation in chemistry?

  Same element is both oxidized and reduced
• What does chlorine produce when it reacts with cold, dilute sodium hydroxide?

  Sodium chlorate (I) solution (NaClO)
• What is the oxidation state of chlorine in Cl₂?


  0
• What is the oxidation state of chlorine in NaCl?

  -1
• What is the oxidation state of chlorine in NaClO?

  +1
• What is sodium chlorate (I) commonly referred to?

  Bleach
• What does hypochlorous acid (HClO) do in water treatment?

  It acts as a powerful disinfectant
• What does chlorine produce when mixed with water?

  Hydrochloric acid (HCl) and hypochlorous acid (HClO)
• Why is hypochlorous acid important in water treatment?

  It ensures clean, safe drinking water
• What are the benefits of using chlorine in water treatment?

  It kills microorganisms and prevents algae growth
• What are the health risks associated with chlorine use?

  Chlorine gas is toxic and can cause burns
• What are disinfection by-products (DBPs)?

  Compounds formed when chlorine reacts with organics
• Why are some DBPs like trihalomethanes (THMs) concerning?

  They are considered carcinogenic
• How are halide ions formed?

  When halogen atoms gain one electron
• What does the reducing power of halide ions refer to?

  The ability to donate electrons to reduce substances
• Which halide is the weakest reducing agent?

  Fluoride
• Which halide is the strongest reducing agent?

  Iodide
• What happens when halide salts react with concentrated H₂SO₄?

  Different products are formed based on halide
• What are the products formed when NaF reacts with concentrated H₂SO₄?

  • HF
  • NaHSO₄
  • Observations: Steamy fumes of HF
• What are the products formed when NaCl reacts with concentrated H₂SO₄?

  • HCl
  • NaHSO₄
  • Observations: Steamy fumes of HCl
• What are the products formed when NaBr reacts with concentrated H₂SO₄?

  1. HBr
  2. Br₂, SO₂, H₂O

  • Observations: Brown fumes of Br₂, colourless SO₂ gas
• What are the products formed when NaI reacts with concentrated H₂SO₄?

  1. HI
  2. I₂, SO₂, H₂O
  3. S, H₂S

  • Observations: Purple fumes of I₂, yellow solid S, rotten egg smell of H₂S
• What is the silver nitrate test used for?

  Identifying halide ions in a solution