What is Group 17 elements?

•  Group 17 comprises of five elements, namely, Fluorine, Chlorine, Bromine, Iodine and Astatine.
• They do not occur free but in the combined state they occur fairly abundantly in nature.
• Fluorine, Chlorine, Bromine and Iodine constitute respectively, 0.06 to 0.09, 0.00016 and 0.00003 per cent of earth’s crust.
• Fluorine, Chlorine, Bromine and Iodine have closely related properties and are known collectively as the Halogens (Greek, halos =sea salts, genes=born) since the salts of the first three occur in sea water.
• On account of their close resemblance and gradual transition of physical and chemical properties the halogens constitute a well-marked group.
• As, is evident the halogens have the general outer electronic configurations ns²p⁵.