Electronegativity of Elements in Modern periodic Table

Introduction

Jöns Jacob Berzelius proposed the word "electronegativity" in 1811. The propensity of an atom of a particular chemical element to draw the shared pair of electrons when a chemical connection is formed is called electronegativity. The symbol for it is X. The bond energy, the direction and strength of a bond's chemical polarity, and other bond properties can all be quantitatively estimated using electronegativity.

It is unusual for the more electronegative atom to fully dominate the bond pair of electrons in covalent bonds where there is a significant difference in the electronegativities of the bound atoms, leading to the creation of two ions. The more electronegative atom creates an anion in this situation, whereas the more electropositive atom transforms into a cation. The nuclear charge, the amount and location of additional electrons in the atomic shells, and other factors all affect electronegativity. Electronegativity increases while travelling from left side to right side throughout a period and decreases when going down in a group.

What is Electronegativity?

The ability of an atom to seize shared electrons in a covalent connection is known as electronegativity. An element's level of electronegativity rises in proportion to how well it attracts the shared electrons. The most electronegative elements are those with the fewest core molecular orbitals between the positively charged nucleus and the valence electrons and the fewest required electrons to complete their valence shells. A specific kind of bond will form depending on the differences in electronegativity between the two bound atoms. When atoms with higher electronegativity differences are joined, they form an ionic bond, and when the electronegativity difference is less the result is a covalent bond.

Polar Bond due to Difference in Electronegativity.

Periodic Trends in Electronegativity

In general speaking, electronegativity rises when going from left to right along a period and falls when moving down a group. As a result, caesium is the least electronegative element, whereas fluorine has the most electronegative nature. The patterns between transition metals and core transition metals are not very smooth. This general rule has a few exceptions. Because of the d-block constriction, germanium and gallium have greater electronegativities than aluminium and silicon, respectively.

Since the 3d-electrons are not active in shielding the higher nuclear charge, the atoms of the fourth immediate aftermath of the first row in the case of transition metals have a short atomic radius. A smaller size of atom correlates with greater electronegativity.

Electronegativity Table

The range of electronegativity values is 0 to 4, which determines whether the final molecule will be polar or nonpolar. For example, sodium and chlorine establish an ionic connection, where chlorine steals an electron, resulting in the formation of the sodium cation (Na⁺) and the chloride anion (Cl^-). The electronegativity value of sodium is 0.93, whereas chlorine has a value of 3.16. Below is a table that contains a list of the elements of the first, second, and third periods with electronegativity values.

Noble Gases are generally not included in any of the trends of the Periodic Table, since each of the Noble gases has a full octet of electrons or a full valence shell.

Atomic Number	Element Name	Symbol	Electronegativity Value
1	Hydrogen	H	2.2
3	Lithium	Li	0.98
4	Beryllium	Be	1.57
5	Boron	B	2.04
6	Carbon	C	2.55
7	Nitrogen	N	3.04
8	Oxygen	O	3.44
9	Fluorine	F	3.98
11	Sodium	Na	0.93
12	Magnesium	Mg	1.31
13	Aluminium	Al	1.61
14	Silicon	Si	1.9
15	Phosphorus	P	2.19
16	Sulfur	S	2.58
17	Chlorine	Cl	3.16
19	Potassium	K	0.82
20	Calcium	Ca	1
21	Scandium	Sc	1.36
22	Titanium	Ti	1.54
23	Vanadium	V	1.63
24	Chromium	Cr	1.66
25	Manganese	Mn	1.55
26	Iron	Fe	1.83
27	Cobalt	Co	1.88
28	Nickel	Ni	1.91
29	Copper	Cu	1.9
30	Zinc	Zn	1.65
31	Gallium	Ga	1.81
32	Germanium	Ge	2.01
33	Arsenic	As	2.18
34	Selenium	Se	2.55
35	Bromine	Br	2.96

Factors Affecting Electronegativity

Here are some factors that affect the electronegativity of an element −

The Oxidation State of the Atom

The electronegativity of an atom increases with an increasing oxidation state. For instance, Fe⁺³has a higher electronegativity than Fe⁺².

Size of the Atom

An atom will have a higher value of electronegativity if it is small in size. In contrast, an atom with a high size will have a lower electronegativity value.

Hybridization of the Atom

The hybridization state has an impact on an atom's electronegativity as well. Greater electronegativity is produced via hybridization with a stronger s-character.

Hybridization State	s-Character	Electronegativity
sp	50%	3.29
sp2	33.33%	2.75
sp3	25%	2.48

Effective Nuclear Charge

With an increase in effective nuclear charge, an atom is more likely to pull the sharing electrons, which raises electronegativity.

Effect of Substituent Attached to the Atom

As opposed to CH₃ I, the C-atom present in CF₃ I gains a larger positive charge. As a result, the C-atom in CF₃ I is much more electronegative than it is in CH₃ I. A change in an atom's electronegativity brought on by substituents alters the atom's chemical behaviour.

Conclusion

Electronegativity means the capacity of an atom to capture shared electrons in a covalent chemical bond. Electronegativity rises when we go from left side to right side in a period and falls when moving down a group. Depending on the differences in electronegativity between the two bound atoms, a particular kind of bond will form.

FAQs

1. What difference in electronegativity is polar?

Before the link is classified as a polar covalent bond, the electronegativity difference typically needs to be at least 0.5.

2. What difference in electronegativity is ionic?

The bond is regarded as ionic if the difference in electronegativity between the two bound atoms is larger than 2.1.

3. Which electronegativity value is the highest?

Fluorine has the highest electronegativity value, i.e., 3.98, and all other measurements of electro-negativities are on a relative scale.

4. Which group exhibits the highest electronegativity?

Halogens have the highest electro-negativities, whereas alkali metals have the lowest.

5. How does acid strength differ depending on electronegativity?

In the periodic table, the degree of acidity rises as electronegativity does across a row. The acidic potency also rises with the loss of electronegativity as we proceed down the group in the periodic table. The size of the atom increases as we move down the group because additional shells are added, and reduces as we move across the period because of the removal of shells.