Electronegativity Definition and Chart
Electronegativity (χ) is a chemical property of an atom or a functional group, to attract electron towards itself. Electronegativity of an atom depends on its Atomic Number and Atomic Radius.
Electronegativity Chart in Periodic Table
In a periodic table Electronegativity increases from left to right and increases from bottom to top. Electronegativity decides how elements bond to each other. The bond can be Covalent Bond, Polar Bond or Ionic bond. The Electronegativity value (Pauling Scale) of some of the common elements are as below:
Hydrogen (H) 2.20
Lithium (Li) 0.98
Beryllium (Be) 1.57
Boron (B) 2.04
Carbon (C) 2.55
Nitrogen (N) 3.04
Oxygen (O) 3.44
Fluorine (F) 3.98
Sodium (Na) 0.93
Magnesium (M) 1.31
Aluminium (Al) 1.61
Sulfur (S) 2.58
Chlorine (Cl) 3.16
Potassium (K) 0.82
Iron (Fe) 1.83
Copper (Cu) 1.90
Silver (Ag) 1.93
Caesium (Cs) 0.79
Gold (Au) 2.54
Mercury (Hg) 2.00
Francium (Fr) 0.7
Bond Types – as decided by Electronegativity
Lets say we have two elements A and B bonded to each other. As regard to the Electronegative values of these two elements, the following cases are observed.
(a) Electronegativity of A and B are same: Then the bonding pair of electrons are midway between A and B. This is ‘Pure’ Covalent Bond.
(b) Electronegativity of B is higher than that of A: Then the bonding pair of electrons are more towards B than A. This is Polar Bond
(c) If Electronegativity of B is too much higher than that of A, the the electron-pair is totally towards B, which is then ionized negatively and A is deprived of electron. This makes A as positive ion. Now the bonding of A and B is due to the electrostatic attraction between Positive-A and Negative-B ions. This is Ionic Bonding.
Electropositivity is the opposite measure which denotes an atom’s tendency to donate electrons. This is metallic character. More the Electropositivity of an element, more is it metallic in nature. For example alkali metals like lithium (Li), sodium (Na), potassium (K), rubidium (Rb), Caesium (Cs), and Francium (Fr) have very low Electronegativity. This means they have higher Electropositivity or metallic character.
Pauling Scale is the Scales for Measuring Electronegativity. It’s range is from 0.79 to 3.98
Flourine: Most Electronegative (3.98 on Pauling Scale)
Caesium: Least Electronegative (0.79 on Pauling Scale)
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