State the occurrence of group-$17$ elements.

(N/A) $(i)$ Fluorine: Fluorine is present mainly as insoluble fluorides such as fluorspar $(CaF_{2})$,cryolite $(Na_{3}AlF_{6})$,and fluoroapatite $[Ca_{9}(PO_{4})_{6} \cdot CaF_{2}]$. Small quantities are also present in soil,river water,plants,and the bones and teeth of animals.
$(ii)$ Chlorine: Sea water contains $2.5 \%$ by mass of sodium chloride. Deposits of dried-up seas contain compounds such as sodium chloride $(NaCl)$ and carnallite $(KCl \cdot MgCl_{2} \cdot 6H_{2}O)$.
$(iii)$ Bromine and Iodine: Apart from sodium chloride,sea water contains bromides and iodides of potassium,magnesium,and calcium (e.g.,$NaBr, KBr, MgBr_{2}$). Iodine is mainly obtained as iodates $(NaIO_{3})$. Certain marine life,such as various seaweeds,contain up to $0.5 \%$ iodine as sodium iodide.
$(iv)$ Tennessine: Tennessine is a synthetic radioactive element with an atomic mass of $294$. Only a small amount has been prepared due to its very short half-life in the millisecond range.