electronegativity


 * Electronegativity**

The term //electronegativity// is defined as the attractive force on electrons caused by the nucleus. Electrons are negatively charged, and the nucleus is positively charged; therefore, opposites attract.





The scale for electronegativity is relative to the most reactive element, fluorine. Linus Pauling set the scale with a maximum value of 4.0 for fluorine, the most electronegative element. All other elements have values less than four, depending on their relative electronegativities in comparison to fluorine.

As you can see from the chart above, there are trends in electronegativity both within columns and within periods (left to right).


 * In general, electronegativity increases from left to right across the periodic table. The reason for this is simply because the number of protons in the nucleus increases as well, but the valence electrons are all within the same energy level with nowhere to go. As the effective nuclear charge increases, so does the pull on the electrons.


 * In general, electronegativity increases from bottom to top in a group. Even though the nuclear charge decreases, another factor comes in to play - the distance between the valence electrons and the nucleus. As valence electrons get closer to the nucleus, they 'feel' its charge getting stronger and stronger. Plus, there are fewer electrons inbetween them and the nucleus that could weaken their attraction (called a 'shielding effect').

Watch this short video on electronegativity trends:

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