Halogens are located in group 17 of the periodic table. Their electronic configurations show increasing atomic numbers and electron shells. The most common oxidation state is -1, with fluorine having the highest electronegativity and tendency to gain electrons. Abundance in the earth's crust and physical properties like size, ionization energy, and melting/boiling points decrease down the group. Hydration energy also decreases as halogen size increases.

1. Halogens and Interhalogens
Dr. Mithil Fal Desai
Shree Mallikarjun and Shri Chetan Manju Desai College Canacona
Goa

2. s
block
d block
p
block
Halogens
f block
Where are Halogens in periodic table?

3. Atomic
number
Halogen Symbol Electronic
configuration
9 Fluorine F [He]2s22p5
17 Chlorine Cl [Ne]3s23p5
35 Bromine Br [Ar] 3d104s24p5
53 Iodine I [Kr] 4d105s25p5
85 Astatine At [Xe] 4f145d106s26p5
Halogens

4. Halogen Electronic
configuration
Oxidation state
F [He]2s22p5 -1, 0
Cl [Ne]3s23p5 -1, 0, +1, +3, +4, +5, +6, +7
Br [Ar] 3d104s24p5 -1, 0, +1, +3, +4, +5, +6
I [Kr] 4d105s25p5 -1, 0, +1, +3, +5, +7
Oxidation state
Most common and stable oxidation state among halogen is -1
as after acquiring one electron they get their octet complete.

5. Halogen Abundance in
earth crust
(ppm)
Relative
abundance
(rank)
F 544 13th
Cl 126 20th
Br 2.5 47th (rare)
I 0.5 62th (rare)
Abundance

6. Halogen Covalent radii
(pm)
Ionic radii (X-)
(pm)
F 72 133
Cl 99 184
Br 114 196
I 133 220
Ionic and covalent radii
Decrease

7. Halogen First Ionisation
Energy (kJ/mol)
Electron
affinity
(kJ/mol)
F 1681 -333
Cl 1259 -349
Br 1143 -325
I 1009 -296
Ionisation energy and electron affinity
Decrease
Fluorine is smaller in size and most electronegative
element

8. Reaction
X-
(g) + nH2O(l) X-
(aq)
(kJ/mol)
F -513
Cl -370
Br -339
I -274
Hydration energy
Decrease
Smaller the size of anion more is the hydration energy

9. Reaction
X-
(g) + nH2O(l) X-
(aq)
(kJ/mol)
F -513
Cl -370
Br -339
I -274
Hydration energy
Decrease
Smaller the size of anion more is the hydration energy

10. Halogen
χp
F 4.0
Cl 3.0
Br 2.8
I 2.2
Electronegativity
Decrease
Electronegativity of H is 2.1, C is 2.5,
N is 3.0 and O is 3.5

11. van
der
Waal
force
of
interaction
increases
Molecule Boiling point
(°C)
Melting point
(°C)
F2 -219 -188
Cl2 -101 -34
Br2 -7 60
I2 114 185
Physical properties

12. Physical characterstics
Halogen (X) Property of X2
Fluorine (F) highly toxic, colorless gas, is the most reactive element
Chlorine (Cl) highly toxic gas, pale yellow-green color. Chlorine is a
very strong oxidizing agent
Bromine (Br) reddish-orange liquid, unpleasant, choking odor.
Iodine (I) Intensely colored solid with metallic luster. volatile,
sublimes when heated (form a violet-colored gas).
Astatine (At) Solid, radioactive

13. Half reaction E°(V)
F2 + 2e- 2F- +2.89
Cl2 + 2e- 2Cl- +1.36
Br2 + 2e- 2Br- +1.08
I2 + 2e- 2I- +0.62
Standard reduction Potential
Decrease
in
reduction
potential