Group 17 Halogens

Group 17 Halogens

Introduction

They are collectively known as Halogens. Group 17(vii A) includes elements Fluorine,chlorine,Bromine,Iodine and Astatin.

Electronic configuration

This is configuration of all elements ns2np5.

Atomic and Ionic size
The halogens have smallest atomic radii in their period because in their period ,the effect becomes maxi. at halogens.
As we go down the group the atomic and ionic radii increases from F to I due to the increasing no. of quantum shells.

Ionisation Enthalpy

Down the group ionisation enthalpy decrease due to increases in atomic size the outermost electron expenses lesser attraction.They shows high value of their ionisation enthalpy because-

1. They have small size.
2. They have greater nuclear charge.
3. They have one electron short than stable nobles gas configuration.

Electron Gain Enthalpy

Down the group electron gain enthalpy decreases is becomes less negative. Halogens have max. electron gain enthalpy in their period because- 1.They have smaller size. 2.They have one electron short than the noble gas configuration ns2np6.

Physical Properties

Fluorine,chlorine are gases ,Bromine is liquid and Iodine is solid . color : All halogens are colored .The is due to the absorption of visible light by their molecules there by causing the excitation of the electrons to higher energy levels and thud produce complementary colors.Colors are as F Cl Br I Light yellow Yellowish green Reddish brown Deep violet

Chemical Properties

Due to this reasons small size, high electronegativity and low bond dissociation energy fluorine is most reactive elements .The reactivity decreases as we move down from Fluorine to Iodine.