Periodic Trend: Electronegativity - Online Tutor, Practice Problems & Exam Prep

Electronegativity, introduced by Linus Pauling, measures an element's ability to attract electrons, differing from electron affinity, which is the energy released when an electron is added to an element. Electronegativity increases from left to right across a period and from bottom to top within a group on the periodic table, with fluorine being the most electronegative element. Transition metals are exceptions due to d and f orbital variations, and noble gases typically lack electronegativity values because they are generally unreactive. Francium is noted as the least electronegative element. Understanding these trends is essential for predicting molecule behavior and bond formation in chemistry.

Periodic Trend: Electronegativity

Electronegativity, abbreviated as EN, is a measurement of an element's ability to attract electrons to itself. Oftentimes it's confused with electron affinity. Electron affinity is different. Electron affinity is the energy released when an electron is added to an element. So remember the distinction here.

In 1932, the American chemist Linus Pauling proposed electronegativity values for the elements. Now this is pretty great. Electronegativity is one of my favorite topics in Gen. Chem, and there's not that many American chemists credited with some of these fundamental concepts. Usually it's people from Russia or Germany or some other country. So it's great to see an American chemist in the form of Linus Pauling getting credit for such an important idea.

Now we're going to say here the periodic trend is electronegativity increases as we move from left to right across a period and going up a group. So as we're heading to this top right corner of the periodic table, electronegativity will increase. Now there of course are exceptions in chem. Those exist with the transition metals because of variations in their D&F orbitals. With these D&F orbitals, there's expansions that happen in shells and this kind of messes up the values of electronegativity.

You'll also notice here that some of the noble gases don't have electronegativity values and that's because they don't want to attract electrons to themselves. We're also going to notice that a lot of the bottom row is blank as well because they're so large, so heavy, they're too unstable to talk about electronegativity. Now in college, what are we all looking to get? That perfect 4.0 GPA.

So fluorine is the most electronegative element on the periodic table. So this is incredibly important to always remember. It is the most electronegative and then francium is the least electronegative element on the periodic table. So just remember, when we talk about electronegativity, it's us attracting electrons to ourselves. When the electron actually adds onto the gaseous state of an element, then that becomes electron affinity.

Periodic Trend: Electronegativity Example 1

Here it says which of the following represents the most electronegative alkaline earth metal. Alright, so this question is actually easier than it appears. You don't need to look at the electronegative values. You don't even need to remember the pattern because there's only one alkaline earth metal presented here.

The only element that's an alkaline earth metal is beryllium. So the answer here is D. But remember the general trend is as we head to the top right corner of the periodic table, our electronegativity will increase. So just keep in mind this general periodic trend for electronegativity.

Between which two elements is the difference in electronegativity the greatest?

• A. C and Si
• B. Li and I
• C. Na and P
• D. K and F
• E. Br and Cl

Arrange the following elements in order of decreasing electronegativity: P, Na, N, Al

• A. P > Na > N > Al
• B. N > P > Na > Al
• C. Na > Al > P > N
• D. N > P > Al > Na
• E. P > N > Na > Al

Here’s what students ask on this topic:

What is electronegativity?

Electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons (or electron density) towards itself when it forms a chemical bond. This concept was first introduced by Linus Pauling in 1932. Electronegativity values are dimensionless because they are derived from the calculated effective nuclear charge on an atom and the distance to its valence electrons.

The most common scale for electronegativity is the Pauling scale, named after its creator. On this scale, the element with the highest electronegativity is fluorine (F), with a value of 3.98, and values range down to cesium (Cs) and francium (Fr), which are among the lowest with values near 0.7.

Understanding electronegativity is crucial for predicting the nature of chemical bonds. Elements with high electronegativity, such as oxygen and nitrogen, tend to attract electrons strongly, while those with low electronegativity, like alkali metals, do not. The difference in electronegativity between atoms in a bond determines the bond's character: large differences usually lead to ionic bonds, while smaller differences lead to covalent bonds.

Why does electronegativity increase across a period?

Electronegativity is the measure of an atom's ability to attract and hold onto electron pairs. As you move across a period on the periodic table, the number of protons in the nucleus of the atoms increases. This means that the positive charge of the nucleus increases, which in turn increases the nucleus's ability to attract electrons towards itself.

Additionally, across a period, the atoms do not gain additional electron shells; instead, electrons are being added to the same energy level. This means that the added electrons are not significantly farther from the nucleus, and the inner shells do not substantially shield the increasing positive charge. As a result, the effective nuclear charge (the net positive charge experienced by electrons in the valence shell) increases.

With a stronger effective nuclear charge, the pull on the valence electrons becomes stronger, making the atom more capable of attracting electrons from other atoms. This is why electronegativity increases as you move from left to right across a period on the periodic table.

Why does electronegativity decrease down a group?

Electronegativity is the measure of an atom's ability to attract and hold onto electrons in a chemical bond. As you move down a group in the periodic table, electronegativity decreases because the atoms become larger due to the addition of electron shells. This increase in atomic radius means that the outermost electrons are farther from the nucleus. Since the positively charged nucleus exerts an attractive force on negatively charged electrons, the greater distance weakens this force. Additionally, the more electron shells there are, the more the inner shells shield the outer electrons from the pull of the nucleus—a phenomenon known as the shielding effect. Because of these factors, the ability of the atoms to attract electrons weakly decreases as you move down a group, leading to a decrease in electronegativity.

Why do noble gases have no electronegativity?

Noble gases, which include elements like helium, neon, and argon, are known for their lack of electronegativity due to their unique electron configurations. Electronegativity is a measure of an atom's ability to attract and hold onto electrons when it forms a chemical bond. In the case of noble gases, they have complete valence electron shells, meaning their outermost electron orbitals are fully occupied.

This full valence shell provides a stable, energetically favorable configuration. Because they are already stable, noble gases have little tendency to gain or lose electrons, and therefore, they do not need to attract electrons from other atoms. This stability is why noble gases are largely inert and do not readily form chemical bonds with other elements. As a result of this lack of bonding tendency, the concept of electronegativity doesn't apply to them in the same way it does to other elements that actively seek to complete their valence shells through bonding. Hence, noble gases are often considered to have no electronegativity.