At the end of the article, you will able to describe Electronegativity Trend Periodic Table. Let’s start our article with the definition. Electronegativity (E.N) is the relative tendency of an atom to attract electrons to itself when chemically combined with another atom in a covalently bonded compound.
Electronegativity Trend Periodic Table
Now, as we know that E.N is defined as the measure of the ability of an atom in a chemical compound to attract electrons.
- Its symbol is χ.
- E.N has no specific units.
- Its value is not constant.
- Value depends upon the nature of an atom with which a particular atom is linked.
If I generalize, in electronegativity trend periodic table, I can say that
- From moving from left to right in a period electronegativity value would increase
- Moving down the group, the E.N value will decrease.
Let’s take a look at the covalently bonded compound something like below diagram.
The one which has a higher E.Nwould just tend to pull the shared pair of electrons towards itself. Now, you should remember this that it will not absorb the electrons totally. It would just shift the electrons towards itself. This is the basic difference if you find out between electron gain enthalpy and E.N.
- Electron gain enthalpy – There is a complete transfer of electron that takes place.
- E.N – It is just the shifting of the shared pair of electrons words itself.
In a periodic table, electronegativity depends on
- The size of an atom.
- The nuclear charge.
Smaller the size higher would be the E.N. Why? Because
- When moving from left to right in a period, the size decreased ( as the number of protons increase). This decrease in size is causing the E.N increase.
- Down to group size increase. Hence, E.N decrease.
Elements in the periodic table with larger atomic radii tend to have lower electronegativities. This is due to the large distance between the nucleus and valence electrons.
- Fluorine element has the highest E.N
- Cesium element has the lowest E.N
Take an example of H2O (water). The E.N of an oxygen atom is more as compared to the Hydrogen. Now, the oxygen has more attracting power than hydrogen.
This results, the shift of electrons. Hence, oxygen acquires a partial negative charge that would be created. Similarly, lack of electrons would result in a partial positive charge on hydrogen. So, these partial charges are the consequence of electronegativity.
Why Trend of Period Increase on moving left to right in a periodic table?
- Generally, elements (like fluorine) that have smaller atomic radii and have high electronegativities will be very reactive and can react violently with other elements.
- For instance, lithium has an electronegativity of .98. Compare that to fluorine, which is across the same period, but has a much higher E.N– 3.98.
Why Trend of electronegativity decrease as you move down a group?
- It is all because of the increased radii and energy levels. It means that there is an increase in distance over which the nucleus has to attract electrons. The greater distance means the protons have less attraction force.
- For example, in Group 2, beryllium’s EN is 1.57, but further, down the group, radium’s EN is .9, which is much lower.
This is about the Electronegativity Trend Periodic Table.