Previous Topic : Co-ordinate Or Co-ionic And Metallic Bonding
Today is the last class session on bonding in chemistry, and today's bonding is Hydrogen Bonding And Vander Waals Force
Hydrogen bonding : is a dipole-dipole attraction which occurs between a hydrogen atom attached to a strongly electronegative atom such as fluorine, oxygen, nitrogen etc.
Note : hydrogen bond is a weak bond but not the weakest and it is strongest in hydrogen fluoride.
Brief : I will explain what electronegative atoms are when we get to electrolysis.
The strongest hydrogen bond is in hydrogen fluoride (HF), meaning that, hydrogen bond cannot be easily broken in hydrogen fluoride (HF).
In other hydrogen bonds, the bond can easily be broken under the influence of heat into simple molecules but in hydrogen fluoride, the hydrogen bond tends to be stronger and even persist in vapour state.
Gaseous hydrogen fluoride (HF) consists mainly of a mixture of H2F2 and H3F3 molecules.
During hydrogen bonding, the highly electronegative atoms attract the shared pair of electrons towards themselves and leaves a partial positive charge in the hydrogen atom and a partial negative charge on the electronegative atom which results into polar molecules.
Please if you won't note anything in this session, please note what I have just writen above.
Another example of hydrogen bonding is water.
Water molecules are held together by hydrogen bonding, below is the bonding structure.
Also Note : The presence of hydrogen bonding in a substance leads to increase in its melting point and boiling point.
Vander Waal's Force
Vander waal's force is the type of force that arises in gases such as Oxygen gas, Chlorine gas, Nitrogen gas, etc. Which are diatomic and non-polar molecules.
Vander waal's force arises from fluctuations in dipole moments of the molecules brought about by motion of electrons around the atomic nuclei.
a] Vander waal's force increases as the number of electrons increases.
b] Vander waal's force is stronger in iodine which is solid at room temperature than in bromine which is liquid at room temperature and less stronger in chlorine which is gas at room temperature.
c] Yes, Vander waal's force is the weakest force of attraction.
That is all on Hydrogen Bonding And Vander Waals Force and on chemical bonding generally. Our next topic is kinetic theory and states of matter.
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