Ionic & Molecular Compounds Electronegativity Susan Baird Dori Delaney Cindy Rothwell

Ionic & Molecular Compounds Electronegativity Bonds form because the positively charged nucleus of each atom attracts the electrons of another atom. However, all elements are not equal: some atoms of elements attract the shared electrons to a much greater extent than atoms of other elements.

Ionic & Molecular Compounds Electronegativity The ability for some atoms to have different attraction abilities is a property that Chemists call electronegativity Electronegativity is the relative measure of an atom’s ability to attract the shared electrons in a chemical bond.

Ionic & Molecular Compounds Trends Electronegativity is a periodic property. As you look across the periodic table, notice that the electronegativity increases until you reach the noble gasses ( the noble gasses do not normally form bonds). As you look down a group notice that the electronegativity decreases. Fluorine has the highest electronegativity. Francium has the lowest electronegativity.

Ionic & Molecular Compounds Take a closer look

Ionic & Molecular Compounds Electronegativity The electronegativity trends on the periodic table are opposite to the trends in the size of atoms. Take a look at the following video: Ionization Energy and Atomic Radius

Ionic & Molecular Compounds Electronegativity and Atomic Radius The trends in size and the trends in electronegativity are opposite. I wonder if size of the atom has anything to do with the atom’s electronegativity? Yes it does! If you look across period 2, from lithium to fluorine the number of protons, electrons and neutrons increases. But the number of shells stays the same. As the number of protons in the nucleus increases, the attractive forces on the electron increase, pulling them closer to the nucleus. Therefore the atom’s radius decreases as you look across periods the periodic table

Ionic & Molecular Compounds Electronegativity and Atomic Radius What does this have to do with electronegativity? This means that the when bonding, the nuclei of nonmetals ( in period two: Carbon, Nitrogen, Oxygen and Fluorine) can attract electrons from another atom more strongly because those electrons can get closer to the nucleus. The valence electrons on metals (Lithium, Beryllium) are farther from the nucleus because the nucleus has a smaller charge then it does for the nonmetals. This means that the metals have a weaker attraction for the bonding electrons.

Ionic & Molecular Compounds Electronegativity A good place to go from here is : Polar and Nonpolar Covalent Bonding Back to Home PageHome Page