Electronegativity: #

Electronegativity is a fundamental concept in chemistry that describes the tendency of an atom to attract a shared pair of electrons in a covalent bond. It is a measure of the atom’s ability to attract and hold onto electrons, and it plays a crucial role in determining the polarity of chemical bonds and the overall molecular properties.

How Electronegativity is Determined #

Electronegativity values are assigned to each element on a scale called the Pauling scale, which ranges from 0.7 (for cesium, the least electronegative element) to 4.0 (for fluorine, the most electronegative element). The electronegativity values of elements are based on various factors, including their atomic size, effective nuclear charge, and electron configuration.

Examples of Electronegativity in Action #

Let’s take a look at some examples of electronegativity in action:

• Example 1: Hydrogen and Oxygen #

  In a water molecule (H₂O), oxygen (O) has a higher electronegativity (3.44) compared to hydrogen (H) (2.20). As a result, the oxygen atom attracts the shared electrons in the O-H bonds more strongly, creating a polar covalent bond. This leads to an uneven distribution of charge in the water molecule, with oxygen being partially negatively charged and hydrogen being partially positively charged, resulting in the formation of hydrogen bonding and unique properties of water, such as high boiling and melting points, high heat capacity, and strong surface tension.

• Example 2: Sodium and Chlorine #

  In a sodium chloride (NaCl) molecule, chlorine (Cl) has a higher electronegativity (3.16) compared to sodium (Na) (0.93). As a result, chlorine attracts the shared electron in the Na-Cl bond more strongly, leading to the transfer of the electron from sodium to chlorine, resulting in the formation of an ionic bond. This creates a crystal lattice structure in solid sodium chloride, with sodium ions (Na+) and chloride ions (Cl-) held together by electrostatic attraction, giving rise to the characteristic properties of ionic compounds, such as high melting and boiling points, electrical conductivity in a molten or dissolved state, and brittleness.

• Example 3: Carbon and Hydrogen #

  In organic molecules, such as hydrocarbons, carbon (C) and hydrogen (H) typically have similar electronegativities. As a result, carbon and hydrogen form nonpolar covalent bonds, where the electrons are shared equally between the atoms, and there is no significant charge separation. This results in the formation of hydrophobic compounds, which do not dissolve in water and exhibit unique properties in organic chemistry, such as the ability to form long carbon chains and complex three-dimensional structures.

#

Electronegativity is an important concept in chemistry that helps us understand the nature of chemical bonds and the properties of molecules. It influences the polarity of covalent bonds, the formation of ionic compounds, and the behavior of organic molecules. By understanding electronegativity, we can better comprehend the behavior of different compounds in various chemical reactions and their impact on the physical and chemical properties of substances.

References #

1. Pauling, L. (1932). The nature of the chemical bond. IV. The energy of single bonds and the relative electronegativity of atoms. Journal of the American Chemical Society, 54(9), 3570-3582.

2. Atkins, P., & de Paula, J. (2009). Atkins’ Physical Chemistry. Oxford University Press.

3. Chang, R. (2017). Chemistry (12th ed.). McGraw-Hill Education.