Group 13 to 18 of the periodic table of elements constitute the p–block. The p–block contains metals, metalloids as well
as non–metals
Fluorine, chlorine, bromine, iodine and astatine are members of Group 17. These are collectively known as the
halogens (Greek halo means salt and genes born i.e., salt producers). The halogens are highly reactive nonmetallic
elements
All the halogens exhibit –1 oxidation state. However, chlorine, bromine and iodine exhibit + 1, + 3, + 5 and
+ 7 oxidation states also. The higher oxidation states of chlorine, bromine and iodine are realised mainly when
the halogens are in combination with the small and highly electronegative fluorine and oxygen atoms e.g., in
interhalogens, oxides and oxoacids
Standard Reduction Potential (SRP)
Anomalous behaviour of fluorine
The anomalous behaviour of fluorine is due to its small size, highest electronegativity, low F- F bond dissociation
enthalpy, and non availability of d orbitals in valence shell. Most of the reactions of fluorine are exothermic (due
to the small and strong bond formed by it with other elements).
Electrolytic method :
CaF2 is treated with concentrated H2SO4 to give an aqueous mixture of HF. This is distilled, giving anhydrous
liquid HF. A cooled solution of KHF2 in anhydrous HF (KHF2 (1 part) + HF (5 part)) is electrolysed using carbon
as anode and steel as cathode in a vessel made of monel metal
CHLORINE (Cl2)
PREPARATION
PREPARATION
PREPARATION
By direct combination of elements
HF. So simple reaction cannot be used
for its preparation, special methods are employed for its preparation.
CHLORINE DIOXIDE
Dichlorine Monoxide
Bleaching powder is also called calcium chlorohypochlorite because it is considered as a mixed salt
of hydrochloric acid and hypochlorous acid
OXY-ACIDS OF HALOGENS
The acid is known only in solution, It is obtained by shaking precipitate of HgO with chlorine water.
It is obtained in aqueous solution when barium chlorite suspension in water is treated with H2SO4. The insoluble
barium sulphate is filtered off
This acid is only known in solution. The acid is prepared by the action of the dilute H2SO4 on barium chlorate
It is the most stable oxy-acid of chlorine. Anhydrous HClO4 is obtained by doing distillation of KCIO4
Pseudo halogens and pseudo halides :
Some inorganic compounds consisting of two or more atoms of which at least one is N have been found to
behave like halogens & they are known as pseudo halogen solids
Group 18 consists of six elements: helium, neon, argon, krypton , xenon and radon . All these are gases and
chemically unreactive. They form very few compounds . Because of this they are termed noble gases
COMPOUNDS OF XENON
XENON TETRAFLUORIDE (XeF4)
XENON HEXAFLUORIDE (XeF6)
XENON–OXYGEN COMPOUNDS
