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# Periodic Trends: Electronegativity

## Measure of the tendency of an atom to attract a bonding pair of electrons.

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Be Electro-Positive!

### How can electronegativity be determined?

Imagine two young children playing with a single ball. This ball can represent a bonding pair of electrons as the children fight over the ball. The electronegativity is symbolized by how greatly each child desires the ball and how strongly he or she grabs onto it. However, keep in mind that an electron is more similar to a cloud than it is to a ball.

Credit: Camera Eye Photography
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Visual of electronegativity [Figure1]

American chemist Linus Pauling developed a system in 1932 for documenting elements’ attraction for electrons in chemical bonds. This is the most commonly used system for determining electronegativity. The most electronegative element, Fluorine, is given a value of 4.0 on the scale while the least electronegative elements, Cesium and Francium, hold values of 0.7.

There are other electronegativity definers as well. In 1934, R.S. Mulliken developed another system to measure electronegativity, known to us as the Mulliken scale. Mulliken created an equation which marks the relationship between Mulliken electronegativity, XM, electron affinity, EAV, and ionization potential IEVXIEV+EAV2\begin{align*}\frac{IE_V+EA_V}{2}\end{align*}

Additionally, the Allred-Rochow scale is another proposal, following Slater's rules with the equation Zeff = Z - S where Z = nuclear charge, S = shielding constant, and Zeff = effective nuclear charge. The scale determines the values of electronegativity (XAR) by using the electrostatic force of attraction between the Zeff and the valence electrons.

### Creative Applications

1. Which electronegativity system do you believe makes the most sense and why?
2. Why does Fluorine have a high electronegativity? Why do Cesium and Francium have low electronegativities?
3. Compare and contrast electronegativity to atomic radii, ionization energy, and electron affinity. What can you come up with? (use the first resource video is necessary)

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