Fluorine is the most electronegative element on the periodic table. Its electronegativity value is 3.98. Cesium is the least electronegative element. Its electronegativity value is 0.79. Electro positivity is the exact opposite of electronegativity, therefore, we can say that Cesium is the most electropositive element.

Those elements requiring only a few electrons to complete their valence shells, and having the least quantity of inner electron shells between the positive nucleus and the valence electrons, are the most electronegative. The most electronegative of all elements is fluorine. Its electronegativity is 4.0. Metals have electronegativities less than 2.0. The least electronegative elements are cesium (Cs) and francium (Fr), with electronegativity values of 0.7.

Therefore,

Fluorine is the most electronegative element and cesium is the least electronegative element.

The strength of a covalent bond is highly dependent on the electronegativities of the two bonded atoms (especially the difference in the electronegativities of the bonded atoms). Homonuclear diatomic molecules feature relatively ‘pure’ covalent bonds since the electronegativities of the bonded atoms are the same (resulting in the bonded pair of electrons being almost equidistant from the two bonded nuclei). Examples of such covalent bonds can be seen in H2 molecules, Cl2 molecules, and O2 molecules. 

On the other hand, the covalent bonds between two species of varying electronegativities tend to become polarized. This occurs because the more electronegative atom pulls the bond pair of electrons closer to itself, developing a partially negative charge in the process (which is usually denoted by the symbol 𝛿-). At the same time, the more electropositive atom develops a partial positive charge (denoted by 𝛿+). These partial charges are responsible for the polarity of the chemical bond. 

In the covalent bonds featuring a large difference in the electronegativities of the bonded atoms, it is uncommon for the more electronegative atom to gain complete control over the bond pair of electrons, resulting in the formation of two ions. Here, the more electronegative atom forms an anion and the more electropositive atom becomes a cation.

It is important to understand that all covalent bonds between dissimilar species have some ionic character. Similarly, all ionic bonds have some covalent character as well. The ionic character of the covalent bond is determined by the difference in electronegativity. When the electronegativities of the bonded species are not very different, the bond will be more covalent than ionic. However, when there is a large enough difference in the electronegativities of the bonded atoms, the bond becomes polar enough to be considered more ionic than covalent. 

Electronegativity is a chemical property that describes the power of an atom in a molecule to attract shared-pair electrons towards itself. There is a large difference in electronegativity for atoms from the left- and right-hand sides of the periodic table. Electronegativity is an important quantity in determining the nature of bonds between elements and will be considered as the main factor in chemical bonding.

The periodic table of elements with the electronegativity table is given below.

A greater atomic size will result in less value of electronegativity, this happens because electrons being far away from the nucleus will experience a lesser force of attraction.

A greater value of nuclear charge will result in a greater value of electronegativity. This happens because an increase in nuclear charge causes electron attraction with greater force.

The electronegativity of an atom depends upon the nature of the substituent attached to that atom. For example, the carbon atom in CF3I acquires a greater positive charge than CH3I. Therefore, C-atom in CF3I is more electronegative than in CH3I. The difference in electronegativity of an atom caused by substituents results in different chemical behaviour of that atom.

Electronegativity is a function of an atom’s ability to attract an electrons binding pair. The most frequently used is the Pauling scale. Fluorine is assigned a value of 4.0, and values that are the least electronegative at 0.7 range down to cesium and francium.

Electronegativity decrease as it moves from top to bottom and increases over time from left to right. The most electronegative element is, therefore, fluorine, while francium is one of the least electronegative elements.

The degree to which an atom attracts electrons in a chemical bond is described by electronegativity. If the difference in electronegativity is greater than 1.7, the character of the bond will be ionic. If the difference in electronegativity is between 0.4 and 1.7, the character of the bond is polar covalent.

The difference between the two is that electronegativity is a chemical property that shows how well an atom can attract electrons to itself as the amount of energy released when an electron is added to a neutral atom.

Electronegativity is an example of an atom’s ability to attract electrons. It is proportional to the difference between the potential for ionization of an atom and its attraction to the electron.

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