Group 7 (Halogens)

Overview of Group 7 (Halogens)

  • Occupying the seventh column in the periodic table.
  • Contains elements like fluorine, chlorine, bromine, iodine, astatine, and tennessine.
  • Halogens have seven electrons in their outermost shell. They can gain an electron to achieve a stable electronic configuration, forming a -1 ion.
  • Follow a predictable pattern of physical and chemical characteristics, known as group trends.

Physical Properties

  • Distinguished by their coloured vapours, going from very pale yellow (fluorine), greenish-yellow (chlorine), to brown (bromine) and purplish-black (iodine).
  • In their pure form, they exist as diatomic molecules (two atoms bonded together).
  • Fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid at room temperature.
  • Their melting and boiling points increase down the group, while the atomic radius and relative atomic mass increase.

Chemical Properties

  • Known for being very reactive, primarily due to their ability to easily gain an electron to complete their outermost shell.
  • Reactivity decreases down the group, with fluorine being the most reactive and astatine the least.
  • Can form salts when combined with metals.

Reactions with Other Elements

  • React with alkali metals (group 1 elements) to form ionic halides.
  • Reaction with hydrogen produces corrosive and poisonous acids, like hydrochloric acid from chlorine and hydrofluoric acid from fluorine.
  • Can displace less reactive halogens from their compounds in a redox reaction.

Uses of Halogens

  • Chlorine is used for water purification and in the manufacture of bleach and plastics.
  • Fluorides are added to toothpaste to prevent tooth decay.
  • Bromine compounds are used as flame retardants.
  • Iodine is a disinfectant and is necessary for the proper functioning of the thyroid gland.

Health and Safety Considerations

  • Halogens are highly toxic and should be handled with care.
  • Eye protection and suitable gloves should be worn when handling these elements or their compounds due to their corrosive nature.
  • Large doses can be harmful and potentially lethal, hence they should be kept out of reach from children and animals.

Investing time in understanding the properties, trends, and applications of halogens will certainly aid in mastering the principles of inorganic chemistry. They represent a very reactive group of elements with significant importance in various areas of science.