Periodic Table of the Elements
Pauling's Electronegativity

Group Period 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1 H 2.1 He 0 2 Li 0.98 Be 1.57 B 2.04 C 2.55 N 3.04 O 3.44 F 3.98 Ne 0 3 Na 0.93 Mg 1.31 Al 1.61 Si 1.9 P 2.19 S 2.58 Cl 3.16 Ar 0 4 K 0.82 Ca 1 Sc 1.36 Ti 1.54 V 1.63 Cr 1.66 Mn 1.55 Fe 1.83 Co 1.88 Ni 1.91 Cu 1.9 Zn 1.65 Ga 1.81 Ge 2.01 As 2.18 Se 2.55 Br 2.96 Kr 0 5 Rb 0.82 Sr 0.95 Y 1.22 Zr 1.33 Nb 1.6 Mo 2.16 Tc 1.9 Ru 2.2 Rh 2.28 Pd 2.2 Ag 1.93 Cd 1.69 In 1.78 Sn 1.96 Sb 2.05 Te 2.1 I 2.66 Xe 2.6 6 Cs 0.79 Ba 0.89 La 1.1 Hf 1.3 Ta 1.5 W 2.36 Re 1.9 Os 2.2 Ir 2.2 Pt 2.28 Au 2.54 Hg 2 Tl 2.04 Pb 2.33 Bi 2.02 Po 2 At 2.2 Rn 0 7 Fr 0.7 Ra 0.89 Ac 1.1 Rf Db Sg Bh Hs Mt Uun Uuu Uub Lanthanides Ce 1.12 Pr 1.13 Nd 1.14 Pm 1.13 Sm 1.17 Eu 1.2 Gd 1.2 Tb 1.1 Dy 1.22 Ho 1.23 Er 1.24 Tm 1.25 Yb 1.1 Lu 1.27 Actinides Th 1.3 Pa 1.5 U 1.38 Np 1.36 Pu 1.28 Am 1.3 Cm 1.3 Bk 1.3 Cf 1.3 Es 1.3 Fm 1.3 Md 1.3 No 1.3 Lr

Explanation:

Linus Pauling analyzed the characteristics of the elements and assigned a number that indicates to the chemist how strongly bonding electrons are held onto by atoms when bonded together in compounds. He named the tendency to attract shared electrons "Electronegativity" and defined that characteristic as "The ability of an atom in a molecule to attract shared electrons to itself". Pauling's calculations were done for all the elements we commonly see bonded. The values are listed above in the periodic table.

The importance of electronegativity is that it tells the chemist the type of bond that forms between two elements. It analyzes each bond -- not the whole molecule (except by looking at all the bonds in the molecule). Bonds are classified according to the Electronegativity difference. If the bond has no difference in electronegativity (such as the bonds in O₂ -- each element has the same electronegativity), then the bond is covalent. The larger the electronegativity difference gets, the more polar the bond becomes. Bond polarities are a continuum -- bonds are usually considered covalent if the electronegativity difference is less that 0.7, polar covalent if the electronegativity is greater than 0.7 but less than 1.7, and ionic if the electronegativity is greater than 1.7.

Electronegativity tends to be strongest in the upper right hand corner of the periodic table (except for the noble gases, which, since they don't bond have an electronegativity of 0) and weakest in the lower left hand corner of the periodic table. This means the Francium Fluoride (FrF) with an electronegativity difference of 3.28 (3.98-0.7) would be the most ionic bond that could be formed.