If you’re studying chemistry, you’ll likely learn about electronegativity. In this guide we’ll break down everything you need to know about electronegativity: what it is, why it matters, how it’s measured, and trends for electronegativity on the periodic table.
Electronegativity Definition
Electronegativity is a chemical property that measures how likely an atom is to attract a shared pair of electrons towards itself in a covalent bond.
Electronegativity is important because it makes bonding between atoms possible. The higher the electronegativity, the greater an atom’s propensity to attract electrons.
Atoms form molecular compounds by combining with other atoms. Electronegativity determines how the bonds between atoms exist. The greater the difference between the electronegativity values of different atoms, the more polar the chemical bond formed between them is.
Electronegativity is not stagnant - it can depend on an atom’s environment. That being said, most atoms display similar electronegativity behavior no matter their environments, so there are common scales used to calculate electronegativity.
How Is Electronegativity Measured?
There are a number of different scales used to calculate electronegativity. The Pauling scale is by far the most common and widely accepted scale for calculating electronegativity and it’s the one that we will use in this article.
The Pauling scale is a method of calculation originally proposed by Linus Pauling. On the Pauling scale, fluorine is assigned an electronegativity of 3.98 and all other elements are given a score relative to that.
Caesium is the least electronegative element on the periodic table (with a Pauling score of 0.79); while fluorine is the most electronegative (3.98).
The other methods of calculating electronegativity are the Mulliken electronegativity scale, the Allred-Rochow electronegativity scale, the Sanderson electronegativity equalization, and the Allen electronegativity scale.
The Allen electronegativity scale is typically considered the simplest way to calculate negativity, though it’s still not the one used most commonly.
Electronegativity Chart
Here is an electronegativity chart for the elements on the periodic table.
The values underneath the elements give their electronegativity as measured by the Pauling scale.
Here are the electronegativity values for some common elements:
|
Element |
Electronegativity, as measured by the Pauling scale |
|
Hydrogen |
2.20 |
|
Carbon |
2.55 |
|
Nitrogen |
3.04 |
|
Oxygen |
3.44 |
|
Fluorine |
3.98 |
|
Sulfur |
2.58 |
|
Chlorine |
3.16 |
Electronegativity Trends
Looking at the chart above, you can see certain electronegativity trends on the electronegativity chart.
Typically, the electronegativity of the elements increases from the bottom of a group to a top. Groups are the vertical columns on a periodic table. If we look at group 1, for instance, you can see Francium (Fr) has an electronegativity of 0.79, while Hydrogen has an electronegativity of 2.20.
Electronegativity also increases from left to right across a period, with the exception of the noble gases. The periods are the horizontal rows on the periodic table. You can see, for instance, in period 3 that Sodium (Na) has an electronegativity calculation of 0.93, while Chlorine (Cl), the last element in that period, has an electronegativity of 3.16.
Sample Electronegativity Questions
There are many different types of questions you can get about electronegativity on an exam. Here are some sample electronegativity questions you might have, as well as answers.
Question 1
Sort the following elements in order of increasing electronegativity using the Pauling scale: barium, calcium, caesium, fluorine
Answer: Caesium, barium, calcium, fluorine
Question 2
On the Pauling scale the electronegativity of nitrogen and oxygen are respectively 3.0 and 3.5.
Why is oxygen more electronegative than nitrogen?
Oxygen has 8 protons in the nucleus while nitrogen only has 7. A bonding pair will experience more attraction from the oxygen's nucleus than from nitrogen's, and so the electronegativity of oxygen is greater.
Final Thoughts
Electronegativity makes bonding between atoms possible. Electronegativity is a chemical property that measures how likely an atom is to attract a shared pair of electrons towards itself in a covalent bond.
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