Electronic Configuration Of Elements To Verify Place In Periodic Table - Session 2

Electronegativity is the ability of and atom in a compound to attract electrons towards itself. Here fluorine is more electronegative. Therefore it tends to attract electrons more towards itself. Can you predict the Electronegativity of an element in the periodic table? In the periodic table, Electronegativity shows two different trends across a group and a period.

In a period, Electronegativity increases from left-to-right. This is because, as the radius decreases, electrons gets closer to the bonding nucleus. In a group electronegativity decreases from top to bottom, or remains the same. This is because, as radius increases, the electrons get farther away from the bonding nucleus.

The Pauling scale  is a numerical scale of electronegativities. It is based on bond- energy calculations for different elements joined by covalent bonds. The electronegativity is a property of an element. It is not a property of an electron. It is the tendency of element to attract electrons towards itself. Pauling scale is used to measure this property.

Fluorine is the most electronegative element in the Universe. It has an electronegativity value of four. An atom of fluorine will attract the bonding pair towards itself. Then it becomes slightly negatively charged.

Electronegativity also explains the formation of an octet in order to gain stability. The most electronegative atoms are near fluorine. This is because they have the least electron shielding and need only 1, 2 or 3 electrons to fill their outermost shell. This is called the octet rule. That is, main-group elements tend to bond in such a way that each atom has eight electrons in its valence shell. This gives them the same electronic configuration as a noble gas. The least electronegative atoms are near Francium. That is because they have the most electron shielding. They will donate 1, 2, or 3 electrons to fulfill the octet rule.

Pauling defined electronegativities based on bond dissociation energies. He defined the difference in electronegativity between atoms A and B, as shown in the equation. This is called the Pauling‘s electronegativity formula. The dissociation energies of bonds AA, AB and BB are expressed in electron volts. In order to make the result dimensionless, eV^-0.5 is used.

The reference point defines the electronegativity of hydrogen as 2.20. The Pauling scale starts from the least electronegative value 0.7 to the most electronegative value 3.98. It is shown in this table. The Pauling scale of electronegativity helps to determine the following. The covalent nature of an element, the position of an element in the EMF series, the dipole moment of molecules and the polarity of bonds. Can you imagine the different effects on Electronegativity as hybridization?.

Hybridization effects and Electronegativity. Hybridization is the concept of mixing two atomic orbitals to create a new type of hybridized orbital. That is, orbitals of different energy, mix up to form orbitals, of equal energy. There are different types of orbitals such as s orbital, p orbital, and d orbital. These orbitals have different shapes and energies. When hybridization occurs, different energy orbitals are mixed, to form orbitals of equal energy.

The Electronegativity rises with the rise of s in hybrid orbitals. This is because s orbitals have greater tendency to attract shared pair of electrons; being nearer to the nucleus. As Electronegativity increases with increasing s hybrid orbital, they make covalent bonds. Lets take example of carbon. It has an increasing electronegativity order from Ethyne, to Ethene and to Ethane. This is because of having 50 percent s is in ethyne, 33.3 percent in ethene and 25 percent in ethane.