3. group 7 the halogens

• What group of the periodic table do halogens belong to?

  Group seven
• What are the physical states of halogens at room temperature?

  Gases, liquids, and solids
• What is the electron configuration of fluorine?

  1s2 2s2 2p5
• What color is chlorine gas?

  Pale green
• What is the physical state of bromine at room temperature?

  Browny orange liquid
• What is the physical state of iodine at room temperature?

  Gray solid
• How do boiling points change as you go down the group of halogens?

  Boiling points increase down the group
• Why do boiling points increase down the group of halogens?

  Due to larger molecules and stronger forces
• What happens to electronegativity as you go down the group of halogens?

  Electronegativity decreases down the group
• Why does electronegativity decrease down the group of halogens?

  Atoms get larger, increasing distance and shielding
• What is the fundamental rule of displacement reactions among halogens?

  • More reactive halogens displace less reactive halides
  • Reactivity decreases down group seven
• What is formed when chlorine displaces bromide ions?

  Bromine and chloride ions
• What color solution is formed when chlorine displaces bromide ions?

  Orange solution
• What color solution is formed when chlorine displaces iodide ions?

  Brown solution
• What happens when bromine reacts with chloride ions?

  No reaction occurs
• What are the four halogens?

  Fluorine, chlorine, bromine, iodine
• What is the physical state of fluorine at room temperature?

  Gas
• What is the physical state of chlorine at room temperature?

  Gas
• What is the physical state of bromine at room temperature?

  Liquid
• What is the physical state of iodine at room temperature?

  Solid
• Why do the boiling points of the halogens increase as you go down the group?

  The molecules and atoms get larger, increasing the van der Waals forces
• Why does the electronegativity of the halogens decrease as you go down the group?

  The atoms get larger, increasing the distance between the nucleus and the bonding electrons
• Which halogen will displace a less reactive halide ion from a solution?

  A more reactive halogen
• What color solution is formed when chlorine reacts with a bromide ion?

  Orange
• What color solution is formed when chlorine reacts with an iodide ion?

  Brown
• What color solution is formed when bromine reacts with an iodide ion?

  Brown
• How is bleach (sodium hypochlorite) produced?

  • Bleach is produced by the reaction of chlorine gas and sodium hydroxide solution
  • The reaction is a disproportionation reaction where chlorine is both oxidized and reduced
  • The overall reaction is:

  Cl2 + 2 NaOH → NaOCl + NaCl + H2O
• What is the purpose of adding chlorine to drinking water?

  To kill bacteria and microorganisms that cause disease
• What are the advantages and disadvantages of chlorinating drinking water?

  Advantages:

  • Destroys microorganisms that cause disease
  • Long-lasting, reduces bacterial buildup
  • Reduces algae growth and discoloration

  
  

  Disadvantages:

  • Chlorine is toxic and can irritate the respiratory system
  • May react with organic compounds to form carcinogenic chloroalkanes
• Why do halide ions make good reducing agents?

  They can easily lose their extra electron, becoming oxidized
• What happens when concentrated sulfuric acid reacts with a halide ion?

  The halide ion reduces the sulfuric acid, producing sulfur dioxide gas
• What are the possible reduction products when halide ions react with concentrated sulfuric acid?

  • Sulfur dioxide (SO2)
  • Elemental sulfur (S)
  • Hydrogen sulfide (H2S)
  • Sodium hydrogen sulfate (NaHSO4)
• Which halide ion is the strongest reducing agent?

  Iodide (I-)
• How does the reactivity of halide ions change as you go down the group?

  The reactivity increases as the ionic radius gets larger and the electron is more easily lost
• How can you test the reducing power of halide ions?

  Two tests:

  1. Reaction with concentrated sulfuric acid
  2. Reaction with silver nitrate solution
• Why can sunlight decompose chlorinated water in swimming pools?

  Sunlight breaks down the hypochlorite ions (ClO-) into chloride ions and oxygen, reducing the disinfecting power
• If you wanted to observe the detailed surface features of a cell, which type of microscope would you use?

  Scanning electron microscope
• What is the formula to calculate the area of a circle with radius $r$?


  $A =$$\pi r^2$
• What is the only compound listed that is not a reduction product of sulfuric acid?

  Sodium hydrogen sulfate
• What are the possible oxidation states of sulfur?

  +6, +4, 0, -2