Chemistry of Halogens
Group 17 of the periodic table contains five elements:
These are named as halogens. The name halogens is derived from two Greek words halo and gens meaning sea salt producers because the first three members occur as salts (chlorides, bromides, iodides) in sea water. These are among the most reactive non-metallic elements. The last member of the family, astatine is a radioactive element.
General characterstics of Halogens:-
- The elements of this group have seven electrons in the outermost shell and have the general electronic configuration ns2np5.
- The halogens have the smallest atomic radii in their respective periods due to maximum effective nuclear charge.
- The ionisation enthalpies of halogens are very high.
- The melting and boiling point of halogens increase with increase in atomic number as we go down the group.
- All these have maximum electron gain enthalpies in their respective periods. They have maximum tendency to accept an additional electron.
- Halogens have large electronegativity values.
- All halogens are non-metallic in character.
- All the halogens are coloured.
- Halogens have only one electron less than the next noble gas. Therefore, they can get the noble gas configuration either by gaining one electron to form uni negative ion, X-, or by sharing electrons with other atoms. Thus, they show an oxidation of state of -1 or +1.