Notes On Group 17: Physical Properties And Oxidation States - CBSE Class 12 Chemistry
Group 17 elements are called halogens.Halogens are the most electronegative elements in the periodic table.

Physical properties:

Physical properties includes Physical state, color, solubility, metallic character, density, melting and boiling point, bond dissociation energy.

Physical state:  The group 17 elements appeared in different physical state
F,Cl are gases
Br is a liquid
I is a solid
All these are diatomic in nature.

Color:  These elements exhibits different colors
F→ Pale yellow color
Cl → Greenish yellow color
Br → Reddish brown color
I → Dark violet color

Solubility:  F,Cl are soluble in water
Br, I are sparingly soluble in water but completely soluble in organic solvents

Metallic nature:  Down the group metallic nature increases.
Due to high ionization enthalpy values all these elements are non metallic in nature.
Down the group non metallic character decreases and Metallic character increases.

Density:  The densities of these elements increases from F to I

Melting and boiling points:  Melting and boiling points of these elements increase regularly from F to I

Bond dissociation energy:  Bond dissociation energies of these elements are gradually decreases from to bottom except for fluorine.

Oxidation states:  General electronic configuration : ns2 mp5
These elements have 7 electrons in their valence shell. they need 1 electron to complete their octet. It can achieved by gaining or by sharing the electron .Hence the common oxidation state of these elements is -1
These elements also exhibits +1,+3,+5 oxidation states along with -1 oxidation state.
Exception: Fluorine exhibits -1oxidation state only because it does not have any d-orbital's in their valence shell.
Cl,Br &I all exhibits different oxidation states +1,+3,+5,+7.This is due to the presence of vacant d-orbital's in their valence shells.
These positive oxidation states are observed in inter halogens, oxides and oxoacids.

Summary

Group 17 elements are called halogens.Halogens are the most electronegative elements in the periodic table.

Physical properties:

Physical properties includes Physical state, color, solubility, metallic character, density, melting and boiling point, bond dissociation energy.

Physical state:  The group 17 elements appeared in different physical state
F,Cl are gases
Br is a liquid
I is a solid
All these are diatomic in nature.

Color:  These elements exhibits different colors
F→ Pale yellow color
Cl → Greenish yellow color
Br → Reddish brown color
I → Dark violet color

Solubility:  F,Cl are soluble in water
Br, I are sparingly soluble in water but completely soluble in organic solvents

Metallic nature:  Down the group metallic nature increases.
Due to high ionization enthalpy values all these elements are non metallic in nature.
Down the group non metallic character decreases and Metallic character increases.

Density:  The densities of these elements increases from F to I

Melting and boiling points:  Melting and boiling points of these elements increase regularly from F to I

Bond dissociation energy:  Bond dissociation energies of these elements are gradually decreases from to bottom except for fluorine.

Oxidation states:  General electronic configuration : ns2 mp5
These elements have 7 electrons in their valence shell. they need 1 electron to complete their octet. It can achieved by gaining or by sharing the electron .Hence the common oxidation state of these elements is -1
These elements also exhibits +1,+3,+5 oxidation states along with -1 oxidation state.
Exception: Fluorine exhibits -1oxidation state only because it does not have any d-orbital's in their valence shell.
Cl,Br &I all exhibits different oxidation states +1,+3,+5,+7.This is due to the presence of vacant d-orbital's in their valence shells.
These positive oxidation states are observed in inter halogens, oxides and oxoacids.

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