4.2.3 Halide Ions

• Halide ions are negative ions formed when halogen atoms in Group 7 gain one electron
• Fluoride ions have the chemical formula $F^{ - }$
• What is the chemical formula of the iodide ion?

  $I^{ - }$
• Steps in the formation of halide ions

  1️⃣ Halogen atom gains one electron

  2️⃣ Formation of a negatively charged ion

  3️⃣ Achievement of a stable octet
• The equation X + e^{ - } \rightarrow X^{ - }</latex> represents the formation of a halide ion.
• The formation of the chloride ion from chlorine involves the gain of one electron
• Halide ions are good reducing agents.
• Which halide ion has the lowest thermal stability?

  Iodide
• Halide ions react with silver nitrate to form insoluble silver halides
• Silver chloride is white and insoluble in water.
• What color is silver iodide?

  Yellow
• Order the reactions of halide ions with concentrated sulfuric acid based on their reducing power:

  1️⃣ Chloride forms HCl gas

  2️⃣ Bromide forms bromine gas

  3️⃣ Iodide forms iodine gas
• The reducing power of halide ions increases as you go down Group 7.
• Halogen atoms achieve a stable octet by gaining an electron
• What does $X$ represent in the equation X + e^{ - } \rightarrow X^{ - }</latex>?


  Halogen atom
• Chlorine gains an electron to form the chloride ion.
• The equation for the formation of the chloride ion is $Cl +$$e^{ - } \rightarrow Cl^{ - }$. The missing reactant is electron
• Match the halogen atom with its corresponding halide ion:

  Chlorine ↔️ Chloride

  Bromine ↔️ Bromide

  Iodine ↔️ Iodide
• Halide ions exhibit both physical and chemical properties.
• The chemical properties of halide ions include their reducing power and reactions with silver nitrate
• Arrange the halide ions in order of increasing reducing power:

  1️⃣ Fluoride

  2️⃣ Chloride

  3️⃣ Bromide

  4️⃣ Iodide
• Halide ions react with both silver nitrate and concentrated sulfuric acid.
• The general equation for the reaction of halide ions with silver nitrate is Ag^{ + }(aq) + X^{ - }(aq) \rightarrow AgX(s)</latex>. The product is an insoluble precipitate
• What is the color of the precipitate formed when chloride ions react with silver nitrate?

  White
• Match the halide ion with the color of its silver halide precipitate:

  Chloride ↔️ White

  Bromide ↔️ Cream

  Iodide ↔️ Yellow
• The reactions of halide ions with concentrated sulfuric acid differ based on their reducing power.
• Which gas is produced when bromide ions react with concentrated sulfuric acid?

  Bromine
• Iodide ions react with concentrated sulfuric acid to produce hydrogen sulfide