Chapter 1: Structure Determines Properties

Electronegativity

• Electronegativity is defined as the ability of an atom to attract electrons towards itself.
• It is one of the most important properties for rationalising and predicting reactivity etc.
• The partial periodic table below has the Pauling electronegativities of some key elements.

• Electronegativity increases left to right across a row in the periodic table   e.g. C < N < O < F

(as you move left to right nuclear charge increases so there is a greater attraction for electrons)
 
• Electronegativity decreases as you move down a group in the periodic table  e.g. F > Cl > Br > I

(each step down a group increases the atomic radii as a "new shell" of electrons are added and the nuclear charge is further shielded by the core electrons, both factors decrease the attraction for electrons)
 
• F is the most electronegative element
  
  
• Metals, e.g. Li and Mg, are less electronegative than C  (i.e. metals are electropositive compared to C)

© Dr. Ian Hunt, Department of Chemistry, University of Calgary