1.2.4-6 - Group 0 + Group 7

Describe the properties of the noble gases.

Non-metals, gases, low boiling points, unreactive (full outer shell; they don’t easily accept or lose electrons).

Discuss the trends in properties as you go down group 0.

The boiling point increases down the group, as the atoms get heavier.

State five characteristics of Group 7.

• 7 electrons in outer shell.

• Colored vapors.

• Diatomic molecules.

• Form ionic salts with metals.

• Form molecular compounds with non-metals.

State Group 7 elements and their states of matter.

• Fluorine, F || F₂ is a pale yellow gas.

• Chlorine, Cl || Cl₂ is a pale green gas.

• Bromine, Br || Br₂ is a dark brown liquid.

• Iodine, I || I₂ is a gray solid.

State three changes that occur in Group 7 as one moves down the group.

• Higher relative molecular mass.

• Higher melting & boiling point.

• Less reactive - less easily gain electrons.

A more reactive halogen displaces a less reactive one from an aqueous solution of its salt; write the equations and state the color change seen when chlorine reacts with sodium bromide and when chlorine/bromine reacts with sodium iodide.

• Cl₂ + 2NaBr → Br₂ + 2NaCl or Cl₂ + 2Br^- → Br₂ + 2Cl^-

  • In this reaction, an orange color of Br₂ would appear.

• Cl₂ + 2NaI → I₂ + 2NaCl or Cl₂ + 2I^- → I₂ + 2Cl^-

• Br₂ + 2NaI → I₂ + 2NaBr or Br₂ + 2I^- → I₂ + 2Br^-

  • In these two reactions, a brown color I₂ of would appear.

A more reactive halogen displaces a less reactive one from an aqueous solution of its salt; explain the trend in reactivity of halogens in these reactions.

Reactivity decreases down the group. As we go down the group, the atoms get larger, so an incoming electron will be less tightly held by the attractive forces from the nucleus. That’s why Cl₂ displaces Br^- and l^-.