At the end of the article, you will able to describe What is Electronegativity. Let’s start discussing it.
What is Electronegativity?
Electronegativity (E.N) – The tendency of an atom to attract electrons towards itself. When two different atoms in a molecule are bonded together by a covalent bond, the electron pair forming the bond is not shared equally by both the atoms.
In other words,
The shared pair of electrons do not lie in the middle of the molecules but shift towards the atom having greater electron affinity.
The tendency of an atom to attract electrons to itself when combined in a compound is called electronegativity.
- To define how much power an atom has to attract electrons, the term E.N used.
- It has no specific units. Also, its value is not constant.
Example of Electronegativity
In the molecule of hydrogen Chloride, electron pair is attracted more towards chlorine. Thus, chlorine is more E.N than hydrogen.
In a polar covalent bond, the shared pair of electrons is attracted by one of the atoms giving partial positive and negative charges to the two atoms. Small atoms attract electrons more than the large ones and are therefore more electronegative.
- The value of E.N depends upon the ionization potential and electron affinity of the atom.
- Low E.N is the characteristic of metals and
- HighE.N is the characteristic of nonmetals.
- Electronegativity increases in going from left to right across the period. It is because atomic size decreases from left to right.
- In a group, atomic size increases hence E.N decreases.
Now, we know What is Electronegativity? Recall that when atoms form covalent bonds, they do not always share their electrons equally. This is because the atoms differ in their E.N, or their ability to attract electrons.
- If the E.N for an atom is high, then it strongly attracts electrons.
- If the E.N for an atom is low, it does not pull at the electrons as much.
We can look at this portion of the periodic table to help visualize the electronegativity of the first several elements.
Non – Polar Electronegativity
Notice the gradient of light blue to the dark blue that indicates the increasing electronegativity of the elements. Look closely at the symbols for Carbon and Hydrogen. Notice that they have similar shading and close E.N values.
- This means that when carbon and hydrogen are bonded together (as shown in this methane molecule) both atoms have a similar ability to attract electrons.
- Neither element pulls more than the other. This type of covalent bond is called a nonpolar bond.
Since the electrons are more or less equally shared between the two atoms. The electronegativities of hydrogen and oxygen are very different. As you can see from the chart, the E.N of oxygen is higher than the electronegativity of hydrogen. Because of this, when oxygen and hydrogen are bonded together (as shown in this water molecule)
- Oxygen pulls at the electrons more than hydrogen does.
- This causes the covalent bond between the oxygen and hydrogen atoms to become polar.
In a polar covalent bond, one of the atoms,
In this case, oxygen has a slightly negative charge since it has a greater affinity for electrons, while the other atom, hydrogen, has a slightly positive charge because its electrons are spending more time around the oxygen atom.
This is all about of your question What is Electronegativity.