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Electronegativity Trends

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Electronegativity is a measure of the ability of an atom in a molecule to attract shared bonding electrons. This property is different from the other ones presented here because it is not relevant for an isolated atom since it deals with shared electrons. A higher electronegativity means that the atom will attract bonded electrons to it more strongly.


The electronegativity of an atom is a measure of the ability of the atom in a molecule to attract shared electrons to itself. Electronegativity values have been calculated for every atom in the periodic table. Electronegativity of an atom reflects its tendency to hold on to and to acquire electrons, the phenomenon arises due to the combination of electron affinities and ionization energies.

Define Electronegativity

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Electronegativity is the ability of an atom or molecule to attract electrons. "Electronegativity is a measure of the ability of an atom in a molecule to attract the shared pair or bonding pair of electron towards itself."
Electronegativity was defined by Linus Pauling in 1932 as a measure of the power of an atom in a molecule to draw electrons to itself. Pauling defined electronegativity as the power of an atom to attract electrons to itself from neighboring atoms in its environment.

Electronegativity Table

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Electronegativity is a measure of a particular atom to attract electrons. The most electronegative atoms are toward the right of the periodic table and these along with hydrogen are the most common bonding partners of carbon. Electronegativity increases from left to right across a row of the periodic table. electronegativity also increases from the bottom to the top of a column.

Electronegativity increases from left to right across the periodic table. The elements in a period essentially have the same shielding but with an increased nuclear charge as one moves across the table. Electronegativity values decrease as one proceeds down a group on the periodic table. The decrease down the group of electronegativity helps explain the difference in elemental properties on groups of the periodic table.

S.No
Group
Electronegativity values
1 CH3
2.3
2
CH2Cl 2.8
3
CH2Cl2 3.0
4
CCl3
3.0
5
CF3
3.4
6
Ph
3.0
7 CH=CH2 3.0
8
C=CH
3.3

The chart of electronegativity is shown in the diagram.

Electronegativity Table

Electronegativity Elements

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The concept of electronegativity is concerned with the attraction for electrons of atoms in molecules. Electronegativity values can be used to estimate the polarity of different bonds. The bonds between elements of widely different electronegativities will be ionic.

The electronegativity of an element is a number that measures the relative strength with which the atoms of the element attract valence electrons in a chemical bond. This electronegativity number is based on an arbitrary scale going from 0 to 4. In general a value of less than 2 indicates a metal.

The values of electronegativity of periodic table elements are represented below.

Electronegativity Elements

The diagram given above represents the elements with highest electronegativities are located in the upper right corner of the periodic table and electronegativities decrease moving down and to the left.

Trends in Electronegativity

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Trends in electronegativity across the period


As we move from left to right in a period, the electronegativity increases. Thus in the third period the electronegativity increases from sodium to chlorine.

On moving across the period, the nuclear charge increases while the atomic radius decreases. Both these factors favor increase in electronegativity.

1st period
Hydrogen (H)
2.1
Helium (He)
-
2nd period
Lithium (Li)
1.0
Beryllium (Be)
1.5
Boron (B)
2.0
Carbon (C)
2.5
Nitrogen (N)
3.0
Oxygen (O)
3.5
Fluorine (F)
4.0
Neon (Ne)
-
3rd period
Sodium (Na)
0.9
Magnesium (Mg)
1.2
Aluminum (Al)
1.5
Silicon (Si)
1.8
Phosphorus (P)
2.1
Sulfur (S)
2.5
Chlorine (Cl)
3.0
Argon (Ar)
-

Trends in electronegativity in groups


As we move down the group the electronegativity decreases. This is because although the nuclear charge increases, there is much more increase in the atomic radius. With increasing distance between the nucleus and the shared pair of electrons, the force of attraction decreases. Hence the electronegativity falls down the group.

The trend in electronegativity is given below.

Element
Electronegativity
Fluorine 4.0
Chlorine
3.0
Bromine
2.8
Iodine
2.5

The Trend for Electronegativity is diagrammatically represented below.

Trends in Electronegativity

Electronegativity Periodic Trend

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The electronegativity of atoms increases as we move from left to right across a period in the periodic table. As we move from left to right across a period the nuclear charge is increasing faster than the electron shielding, so the attraction that the atoms have for the valence electrons increases.

The electronegativities of atoms decreases as we move from top to bottom down a group in the periodic table. Because as we go from top to bottom down a group, the atoms of each element have an increasing number of energy levels. The electrons in a bond are thus farther away from the nucleus and are held less tightly.

Electronegativity $\overset{increases}{\rightarrow}$ Across a period - Left to right in the periodic table

Electronegativity $\overset{decreases}{\rightarrow}$
Down the group - Top to bottom in the periodic table

The Electronegativity Trend Periodic Table is diagrammatically represented below.

Electronegativity Periodic Trend
Electronegativity is a periodic property.
  1. It generally increases with increase in atomic number.
  2. It generally increases with increase in atomic weight.
  3. It increases with increase in nuclear charge.
  4. It increases with decrease in atomic radii.