Chemistry
(a) What is the name given to group 17 elements? Why are they called so?
(b) Comment on the (i) reactivity (ii) colour and (iii) physical state of group 17 elements.
Answer
(a) Group 17 elements are called halogens. The name halogen (Greek, halo = sea or salt + gen = producing) means 'salt former'. Group 17 elements form salts, hence, they are called Halogens.
(b) (i) Halogens are the most reactive non-metals. Their reactivity decreases down the group. For example: fluorine is the most reactive and iodine is the least reactive.
(ii) The intensity of the colour of the element increases from pale to dark. Fluorine is a pale yellow gas, chlorine is a greenish-yellow gas, bromine is a reddish-brown liquid and iodine is a violet solid.
(iii) The physical state of the elements changes from gas to solid as we move down the group. Fluorine is a gas, chlorine is a gas, bromine is liquid and iodine is solid.
Related Questions
Give reasons.
(a) Alkali metals are kept in inert solvent.
(b) Alkali metals and halogens do not occur free in nature.
(c) Alkali and alkaline earth metal compounds usually form electrovalent compounds.
(d) Inert gases do not form compounds.
(a) State the nature of compounds formed when group 17 elements combine with (i) metals (ii) non-metals.
(b) Why group 17 elements are highly reactive?
State the uses of Modern Periodic table.
Give the merits of Mendeleev's periodic table.