What is electronegativity | Chemistry | Electronegativity IIT JEE | Electronegativity NEET
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 Published On Mar 25, 2020

This video will help you to learn What is electronegativity? Along with Example questions from Electronegativity IIT JEE and Electronegativity NEET exams.
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What is electronegativity âť“

Electronegativity is a measure of the tendency of an atom to attract electrons towards itself in a molecule or compound. Since it is relative, it does not have any unit.

Different factors affecting electronegativity in periodic table are:-

1 - Atomic Size or Radius: Electronegativity of a bonded atom decreases with an increase in its size. Shielding effect is directly proportional to atomic size, therefore, electronegativity increases with decrease in the shielding effect

2 - Effective Nuclear Charge: When an effective nuclear charge is high the nucleus will attract the shared electrons with greater strength and the electronegativity will be high

3 - Hybridization state of an atom : Electronegativity in periodic table increases with increase in the s-character of the hybrid orbital. This happens because the s-orbital is nearer to the nucleus and thus feels greater attraction resulting in an increase in electronegativity.

4 - Bond Order: The number of covalent bonds presents between two bonded atoms is known as bond order. With an increase in the bond order, the bond distance decreases effective nuclear charge increases and therefore electronegativity increases. The increasing order of electronegativity is single bond less than double bond less than triple bond.

5 - Oxidation Number : The electronegativity value increases with the increase in oxidation number because the radius of an atom decreases with an increase in its oxidation number.
For example, the order of electronegativity for the three oxidation states of Iron is as follows: Fe3+ greater than Fe 2 + greater than Fe

Periodic trends of Electronegativity

i) Atomic size decreases on going from left to right in a period therefore electronegativity increases. In a period, the electronegativity value of a halogen is maximum, while the electronegativity value of an alkali metal is minimum.

ii) Atomic size increases on going from top to bottom in a group therefore electronegativity decreases.For example, oxygen has a higher electronegativity than sulphur

iii) The electronegativity value of inert gases is zero because they do not form any covalent bond

Exceptions to the general trend of electronegativity in periodic table

1 - The elements of group 2 B that is Zinc, Cadmium and Mercury show increase in electronegativity value on going from top to bottom in the group.

2 - The elements of group 3 A, which are Aluminium to Galium show increase in electronegativity value on going from top to bottom in the group.

3 - The elements of group 4 A show no change in electronegativity value on going from
top to bottom in the group from Silicon on words.

Measurement of Electronegativity Difference Value

Pauling Scale of electronegativity

Linus Pauling was the first scientist to put forward the concept of electronegativity and created a scale to measure electronegativity and bond polarity

Fluorine is the most electronegative element with an assigned a value of 4.0 and electronegativity values range down to caesium and francium which are the least
electronegative elements at 0.7

Mulliken Scale of electronegativity

Mulliken Suggested that the electronegativity value should be calculated as the average of ionisation enthalpy and electron gain enthalpy.

We hope this video will improve your understanding of this concept. Thanks for watching this video.

Chapters:
0:00​ What is electronegativity
0:25 Factors affecting electronegativity in periodic table
2:20 electronegativity trends
3:36 Exceptions of electronegativity trends on periodic table
4:11 Measurement of electronegativity difference
4:37 Pauling Scale of electronegativity
4:57 Mulliken Scale of electronegativity

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