Electronegativity

Introduction

Electronegativity is the ability of an atom or any individual atom to attract(force) shared electrons (e_-) or electron density while forming a bond(chemical). The electronegativity of any individual atom can be affected by two factors, and they are- its atomic number (Z) and the distance(separation) at which its valence (complete octet) electrons stay from (away) the charged nucleus.

We can also determine the electronegativity of an atom with the help of some factors like nuclear charge, the number of electrons in the atomic shell, etc. Generally, electronegativity increases when we move or go from left (l) to right (r) in the periodic table (p.t) and it decreases on going down a group.

So, it is found that fluorine (F) is the most (maximum) electronegative type element presents in the periodic table and, caesium is the minimal electronegative (type) element present in the periodic table. But, still, there are some or few exceptions (against) to this general trend or rule. Gallium (Ga) and germanium (Ge), these elements have higher electronegativities when compared to aluminium (Al) and silicon (Si) respectively.

What is Electronegativity?

Electronegativity is the capability of any individual atom to attract the shared electron pairs or, electron density while forming or joining a bond(chemical). The electronegativity of an atom can be affected by two major factors and those factors are- atomic number (Z) and the distance(separation) at which its valence electrons (e^-) reside or are found from the charged nucleus. The higher (maximum) the electronegativity, the more (higher) an atom or its substituent group (side groups) attracts electrons (e^-). Electronegativity directly helps in the estimation of bond energy (B.E), and the sign (‘+’ or ‘-’) and the magnitude (numeric) of a bond’s chemical type polarity. Electronegativity can be determined by some factors like the nuclear charge of an atom, the number of other (rest) electrons in the shell (atomic), and the location or position of other electrons in the atomic orbital. Electronegativity follows some general trends that include electronegativity exceeding or increasing on moving or roaming from left (l) to right (r) in the periodic table (p.t) and reducing or decreasing on moving down a group.

Periodic trends in Electronegativity

Generally, electronegativity decreases down the group and increases on moving from left (l) to right (r) along a period. So, it is found that fluorine (F) has the highest electronegativity in the periodic table and, caesium has the least or minimum electronegativity in the same periodic table. Therefore, the compound called caesium fluoride has the most(maximum) ionic character. Although there are certain exceptions and those are gallium (Ga) and germanium (Ge). Since, they have higher (more) electronegativities than aluminium (Al) and, silicon (Si) respectively. This is due to the d-block or d-orbital contraction. Also, the elements of the fourth (4th) period, just after the first (1st) row of the transition type metals have abnormally smaller atomic radii this is again due to the d-orbital contraction. That means here the 3d-electrons (e^-) are not effective or capable of shielding or covering the increased (exceeded) nuclear charge and as we know smaller size correlates or relates with higher electronegativity. One another abnormality is the high electronegativity of lead (Pb) as compared to thallium (Th) and bismuth (Bi).

Physchim62, Periodic variation of Pauling electronegativities, CC BY-SA 3.0

Electronegativity Table

As we know, electronegativity is the capability of an atom (individual) to attract the shared pairs of an atom or group of atoms. There is a huge electronegativity difference between the atoms found on the left-hand side and the atoms present on the right-hand side of the periodic table (p.t). Electronegativity is also very important or useful in determining the types of bonds between the elements and this is also considered one of the important factors in chemical bonding. And, as we know the electronegativity of an atom increases when we move towards the right in the periodic table (p.t), also its electronegativity increases when we move up in the periodic table. So, the atoms present at the top right (t-r) of the periodic table have the highest electronegativities and the atoms present at the bottom left of the table have the lowest electronegativities.

Factors Affecting Electronegativity

Following are some factors affecting the electronegativity −

• Nuclear charge- Electronegativity is directly proportional to the nuclear charge. The greater the value of nuclear charge, the greater will be its electronegativity. This relation occurs because whenever there is an increase (exceed) in the nuclear charge, electrons get attracted with a greater (larger) force.

• Size of an atom- Electronegativity is inversely proportional to the atomic size of an atom. That is greater the atomic size, the fewer the value (magnitude) of electronegativity. This relation occurs because electrons (e^-) reside far away (large distance) from the nucleus and thus experience less forces of attraction.

• Substituent’s effect- The Electronegativity of an atom also depends (or changes) upon the nature (type) of the substituent that is attached (joined) to that atom. For ex- In CF₃ I, the carbon atom will acquire a greater positive (+) charge as compared to CH₃ I. That’s why carbon atoms in the CF₃ I are more electronegative than the carbon atoms in CH₃ I.

Conclusion

Electronegativity is nothing but the tendency or capability of an atom to attract shared electrons or electron density while forming a bond (chemical bond). The electronegativity of any individual atom can be affected or hampered by both its atomic number (Z) and the distance at which its valence electrons stay from the charged nucleus. We can also determine the electronegativity of an atom with the help of some factors like nuclear charge, the number of electrons in the atomic shell, etc. Generally, electronegativity increases when we move from left (l) to right (r) in the periodic table (p.t) and it decreases on moving or going down a group. So, it is found that fluorine (F) is the most electronegative element found in the periodic table and, caesium is the least electronegative element in the periodic table. Although there are some exceptions like gallium, germanium, lead, etc.

FAQs

1. What do you mean by electronegativity?

Electronegativity can be defined as the capability of any individual atom to attract shared electrons or electron density towards itself while forming a bond (chemical bond).

2. Who has discovered electronegativity?

Electronegativity has been discovered by an American scientist named Linus Pauling.

3. What are the factors affecting electronegativity?

Some of the factors affecting electronegativity are- the size of an atom, nuclear charge, and the nature of the substituent.

4. How does electronegativity depend on the factors?

Electronegativity is directly proportional to the nuclear charge and to the nature of the substituent attached with it. And electronegativity is inversely proportional to the size of an atom.

5. What do you mean by the periodic trends of electronegativity?

Generally, electronegativity decreases down the group and increases on moving from left to right along a period. So, it is found that fluorine (F) has the highest electronegativity in the periodic table and, at the same time caesium has the least or minimum electronegativity in the same periodic table.