Electronegativity - Overview, Factors, Elements, Applications, FAQs
The electronegativity meaning of an atom was described by Linus Pauling in 1931 as the atom's tendency to attract electrons to itself when joined in a compound. Pauling and others have tried to link the difference in electronegativity between two atoms to the amount of ionic character in their relationship. Generally, small atoms attract electrons more strongly than large ones, and hence small atoms are more electronegative. Electronegativities are higher in atoms with nearly filled electron shells than in those with sparsely inhabited ones.
What is Electronegativity?
Electronegativity definition as the measure of ability of an atom or atoms involved in covalent bonding s to attract shared electrons to itself. It measures how strongly atoms attract bonding electrons to themselves. It is represented by the Greek letter chi ‘χ’.
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Scales on Electronegativity
In 1932, Linus Pauling proposed the idea of electronegative elements. As per Pauling scale of electronegativity Fluorine has an electronegativity of 3.98 on the Pauling scale, and the other elements are scaled in relation to it. Linus Pauling created most often used scale. Fluorine has highest electronegativity element on this scale, whereas it is the least electronegative element, with a value of 0.7. Electronegative elements scales include Mulliken scale, which averages first ionisation energy as well as electron affinity. It was propose by Robert S. Mulliken in 1934.
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The electrostatic attraction between an atom's nucleus and its valence electrons is measured using the Allred-Rochow scale. Thus, the element with highest electronegativity is Fluorine.
How to find Electronegativity: Pauling scale Formula of Electronegativity
Looking at a hypothetical molecule XY is the best way to explain Pauling’s method of electronegativity. We may explain relative affinities of two atoms by each other with comparing and measuring X-Y bond energy along with some theoretical X-Y bond energy (estimated as the mean of X-X and the Y-Y bond energies).
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Δ Bond Energies = (X-Y) measured – (X-Y) expected
If X and y have the identical electronegativities, the measured bond energy is equal to the theoretical (anticipated) bond energy, and the bond energies are zero.
If these atoms' electronegativities differ, we'll witness a polar molecule in which one atom begins to pull electron density toward itself, causing it to become largely negative.
The value ranges for Pauling's scale of the electronegative elements beginning from Fluorine (most electronegative to Francium (least electronegative). Furthermore, if the difference in electronegative elements between two atoms is considerable, the bond type tends to be more ionic; whereas, if the difference in electronegative elements is minor, the bond type tends to be more covalent.
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Electronegativity and the periodic table:
Periodic Trends in the Electronegativities of Elements
Electronegativity of elements across a period: As we move from left to right through a period in the modern periodic table, the nuclear charge increases and the atomic size decreases, increasing the value of electronegative elements.
Electronegativity example: Electronegativity trend across period three in the periodic table is shown as. Thus, the most electronegativity atom is Chlorine here.
Electronegativity of elements down a group:
The atomic number grows as we progress down the group on the current periodic chart. The nuclear charge also rises, but the effect is lessened by the addition of one shell. As a result, the value of electronegativity falls as we progress down the group.
Example: Electronegativity of halogen group decrease as we move down the group from fluorine to astatine and it is shown in the diagram below.
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Metals have low electronegativity values as compared to the non-metals. Hence, metals are considered electropositive whereas non-metals are considered electronegative.
Most and Least Electronegative Elements:
Fluorine has the highest electronegativity element on periodic table. The electronegativity value is 3.98 and so the cesium is least electronegative element thus, electronegativity value is 0.79, and therefore it is said that Cesium is the most electropositive element while Fluorine is the least electropositive element. Negativity meaning is the tendency to pull bond pair of electrons closer to itself.
Periodic table carrying the electronegativity of elements is known as the electronegativity table and is given as:
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The above table shows electronegativity periodic table.
Factors Affecting Electronegativty:
Atomic Dimensions: The force of attraction between electrons and the nucleus is weaker because electrons are further away from the nucleus. The value of electronegativity diminishes as atomic size rises.
Nuclear Charge: As the nuclear charge of a substance grows, so does its electronegativity. This happens because as nuclear charge rises, so does electron attraction.
Effect of Substituent: The electronegativity of an atom is determined by the type of substituent attached to it. The positive charge of the carbon atom in CF3I is higher than that of the carbon atom in CH3I. As a result, CF3I' s C atom is more electronegative than CH3I's C atom. Substituents affect the electronegativity of an atom, which changes the atom's chemical behaviour.
Application of Electronegativity:
The idea of electronegativity is used in predicting whether bonds between similar or dissimilar atoms is non-polar covalent bond, polar covalent bond (or) ionic bond.
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