Question

Sea is the greatest source of halogens. Comment.

Answer 1

Halogens are the elements of group $17$ in the periodic table. These elements are very reactive. Because of this reason it becomes difficult for them to occur freely in nature and so their compounds are widely distributed. And most of them occur in
sea water and marine life also.

Complete answer:
Sea water is the water from the sea. The amount of dissolved salt in the sea water is very high which makes it saline in nature. Sea water or salt water contains many ions in it. The ions include chlorides, bromides and iodides of$Na,{\text{ }}K,{\text{ }}Mg,{\text{ }}and{\text{ }}Ca$. The main ion present in the seawater is$NaCl$. The deposits of dried up sea bed also contain sodium chloride iodine and carnallite, $KCl.MgC{l_2}.6{H_2}O$. Even marine life contains iodide in their system. For example- seaweed contains $0.5\%$ iodine as sodium iodide $\left( {NaI} \right)$ and Chile saltpeter also contains about $\left( {0.3\% } \right)$of sodium iodate. Because of all of these it can be said that the seawater is a treasure of many elements which include halogens as well. So thus this also concludes that sea water is the greatest source of halogens.
Since ancient times, sea water has been used as a source for obtaining minerals. And now minerals are extracted from sea water. There are four most concentrated minerals that are extracted commercially. These minerals are $Na,{\text{ }}K,{\text{ }}Mg,{\text{ }}and{\text{ }}Ca$. Mineral elements with low concentrations have not been recovered from seawater because their market values are much lower than the capital and operational costs of extraction. During the seawater extraction process, many minerals occur as by-products in the exhausted brine. These minerals are then recovered economically.

Note:
Apart from sea water, volcanoes are also considered to be a good source of halogens. Among them chlorine and fluorine are present in the largest quantities. But large quantities of halogens only produced from the sea water and sea life as well.