The highest electronegativity in the periodic table

After studying this page, you should be able to:

describe and explain the trend in electronegativity across period 3

The table shows electronegativity values for the elements Na to Ar.

Element	Symbol	Atomic number	Electronegativity
sodium	Na	11	0.93
magnesium	Mg	12	1.31
aluminium	Al	13	1.61
silicon	Si	14	1.90
phosphorus	P	15	2.19
sulfur	S	16	2.58
chlorine	Cl	17	3.16
argon	Ar	18	—

Electronegativity is the ability of an atom to attract the bonding electrons in a covalent bond.

The table gives values on the Pauling scale, which have no units. Fluorine (3.98) is the most electronegative element.

Electronegativity in the periodic table

The graph shows how electronegativity varies across period 3:

as the atomic number increases, the electronegativity of the elements increases.

Going across period 3:

the nuclear charge increases …
the atomic radius decreases …
there are more electrons, but the increase in shielding is negligible because each extra electron enters the same shell …
so electrons will be more strongly attracted to the nucleus.

In Period 3, sodium with 11 protons is the least electronegative element, and chlorine with 17 protons is the most electronegative element. You might expect argon (with 18 electrons) to be the most electronegative element in Period 3. However, it does not form covalent bonds, so it does not have an electronegativity value.

Thank you to Ismail Abebanjo from Nigeria for pointing out an error on this page.
It is now corrected!

What is the most electronegative element? Electronegativity is one measure of an element's ability to form chemical bonds by attracting an electron. Here is a look at the most electronegative element and an explanation for why it has such high electronegativity.

Fluorine is the most electronegative element. Fluorine has an electronegativity of 3.98 on the Pauling Electronegativity Scale and a valence of 1. A fluorine atom needs one electron to fill its outer electron shell and achieve stability, which is why free fluorine exists as the F- ion. Other highly electronegative elements are oxygen and chlorine. The element hydrogen does not have as high of electronegativity because, although it has a half-filled shell, it readily loses an electron rather than gains one. Under certain conditions, hydrogen does form the H- ion rather than H+.

In general, all elements of the halogen element group have high electronegativity values. The nonmetals to the left of the halogens on the periodic table also have fairly high electronegativities. Elements belonging to the noble gas group have very low electronegativity values because they have complete valence electron shells.

Most Electropositive Element: The opposite of electronegativity is electropositivity. Learn which element is the most electropositive or has the lowest electronegativity.
Electronegativity Periodic Table: This handy table lists all of the electronegativity values of the elements. The values can be used to predict whether two atoms will form ionic or covalent bonds.
Periodic Table Trends: Electronegativity is one of the trends seen in the organization of the elements in the periodic table.

Figure \(\PageIndex{1}\) (Credit: (left) Image copyright Pressmaster, 2013; (right) Image copyright cdrin, 2013; Source: http://www.shutterstock.com(opens in new window); http://www.shutterstock.com/(opens in new window); License: Used under licenses from Shutterstock.com)

Have you ever noticed how some people attract others to them? Whether it be their personality, attractiveness, or athletic skills—something pulls people toward them; while others have a smaller group of friends and acquaintances. Atoms do the same thing. One atom may pull electrons strongly to it, while a second type of atom has much less "pulling power".

Valence electrons of both atoms are always involved when those two atoms come together to form a chemical bond. Chemical bonds are the basis for how elements combine with one another to form compounds. When these chemical bonds form, atoms of some elements have a greater ability to attract the valence electrons involved in the bond than other elements.

Electronegativity is a measure of the ability of an atom to attract the electrons when the atom is part of a compound. Electronegativity differs from electron affinity because electron affinity is the actual energy released when an atom gains an electron. Electronegativity is not measured in energy units, but instead a relative scale. All elements are compared to one another, with the most electronegative element, fluorine, being assigned an electronegativity value of 3.98. Fluorine attracts electrons better than any other element. The table below shows the electronegativity values for the elements.

Figure \(\PageIndex{2}\): The electronegativity scale was developed by Nobel Prize winning American chemist Linus Pauling. The largest electronegativity (3.98) is assigned to fluorine and all other electronegativity measurements are on a relative scale. (Credit: Christopher Auyeung; Source: CK-12 Foundation; License: CC BY-NC 3.0(opens in new window))

Since metals have few valence electrons, they tend to increase their stability by losing electrons to become cations. Consequently, the electronegativities of metals are generally low. Nonmetals have more valence electrons and increase their stability by gaining electrons to become anions. The electronegativities of nonmetals are generally high.

Electronegativities generally increase from left to right across a period. This is due to an increase in nuclear charge. Alkali metals have the lowest electronegativities, while halogens have the highest. Because most noble gases do not form compounds, they do not have electronegativities. Note that there is little variation among the transition metals. Electronegativities generally decrease from top to bottom within a group, due to the larger atomic size.

Of the main group elements, fluorine has the highest electronegativity (EN \(= 4.0\)) and cesium the lowest (EN \(= 0.79\)). This indicates that fluorine has a high tendency to gain electrons from other elements with lower electronegativities. We can use these values to predict what happens when certain elements combine.

When the difference between atom electronegativities is greater than ~1.7, then a complete exchange of electrons occurs. Typically this exchange is between a metal and a nonmetal. For instance, sodium and chlorine will typically combine to form a new compound and each ion becomes isoelectronic with its nearest noble gas. When we compare the EN values, we see that the electronegativity for \(\ce{Na}\) is 0.93 and the value for \(\ce{Cl}\) is 3.2. The absolute difference between ENs is \(\left| 0.93 - 3.2 \right| = 2.27\). This value is greater than 1.7, and therefore indicates the occurence of a complete electron exchange.

Summary

Electronegativity is a measure of the ability of an atom to attract the electrons when the atom is part of a compound.
Electronegativity values generally increase from left to right across the periodic table.
Electronegativities generally decrease from the top to bottom of a group.
The highest electronegativity value is for fluorine.