Electronegativity and Bond Polarity Chemistry Tutorial
Key Concepts
Electronegativity
- Electronegativity is the relative tendency of a bonded atom to attract electrons to itself.
- An atom with extremely low electronegativity, like a Group 1 (IA) or alkali metal, is said to be electropositive since its tendency is to lose rather than to gain, or attract, electrons
- Electronegativity decreases down a Group in the Periodic Table as the atomic radius and number of inner electron shells both increase.
- Electronegativity increases across a Period of the Periodic Table, in general, due to increasing nuclear charge and decreasing atomic radius.
- For the commonly encounted atoms in High School Science, the order in decreasing electronegativity is
F > O > N ≈ Cl > Br > C ≈ S ≈ I > P ≈ H > Si
1 H 2.1 |
The number on top of the element's symbol is its atomic number, Z (the number of protons in the nucleus). In the middle of the box there is a letter (or letters), the symbol for the element. The number underneath the symbol is the electronegativity of the element using Pauling's method. |
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| Period | Group 1 |
Group 2 |
Transition Metals | Group 13 |
Group 14 |
Group 15 |
Group 16 |
Group 17 |
Group 18 |
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| 1 | 2 He - |
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| 2 | 3 Li 1.0 |
4 Be 1.5 |
5 B 2.0 |
6 C 2.5 |
7 N 3.0 |
8 O 3.5 |
9 F 4.0 |
10 Ne - |
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| 3 | 11 Na 0.9 |
12 Mg 1.2 |
13 Al 1.5 |
14 Si 1.8 |
15 P 2.1 |
16 S 2.5 |
17 Cl 3.0 |
18 Ar - |
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| 4 | 19 K 0.8 |
20 Ca 1.0 |
21 Sc 1.3 |
22 Ti 1.5 |
23 V 1.6 |
24 Cr 1.6 |
25 Mn 1.5 |
26 Fe 1.8 |
27 Co 1.9 |
28 Ni 1.9 |
29 Cu 1.9 |
30 Zn 1.6 |
31 Ga 1.6 |
32 Ge 1.8 |
33 As 2.0 |
34 Se 2.4 |
35 Br 2.8 |
36 Kr - |
| 5 | 37 Rb 0.8 |
38 Sr 1.0 |
39 Y 1.2 |
40 Zr 1.4 |
41 Nb 1.6 |
42 Mo 1.8 |
43 Tc 1.9 |
44 Ru 2.2 |
45 Rh 2.2 |
46 Pd 2.2 |
47 Ag 1.9 |
48 Cd 1.7 |
49 In 1.7 |
50 Sn 1.8 |
51 Sb 1.9 |
52 Te 2.1 |
53 I 2.5 |
54 Xe - |
| 6 | 55 Cs 0.7 |
56 Ba 0.9 |
57 La 1.1 |
72 Hf 1.3 |
73 Ta 1.5 |
74 W 1.7 |
75 Re 1.9 |
76 Os 2.2 |
77 Ir 2.2 |
78 Pt 2.2 |
79 Au 2.4 |
80 Hg 1.9 |
81 Tl 1.8 |
82 Pb 1.9 |
83 Bi 1.9 |
84 Po 2.0 |
85 At 2.2 |
86 Rn - |
| 7 | 87 Fr 0.7 |
88 Ra 0.9 |
89 Ac 1.1 |
104 Rf - |
105 Ha - |
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Bond Polarity
- Identical non-metallic atoms have identical electronegativities and form non-polar covalent bonds since the bonding electrons will be shared equally between the atoms in the molecule.
- When atoms of similar, but different, electronegativities (a difference < ~1.7) bond, the more electronegative atom has a greater share of the bonding electrons than the less electronegative atom. The more electronegative atom has a partial negative charge, and the less electronegative atom has a partial positive charge. The resulting covalent bond is called a polar covalent bond.
- Non-metals are more electronegative than metals. When an extremely electronegative atom, like fluorine, bonds with an electropositive atom, like sodium, the resulting bond is ionic due to the huge difference in electronegativity (difference > ~1.7). The electronegative atom's pull on the bonding electrons is so strong that it pulls the bonding electron off the electropositive atom resulting in two oppositely charged ions which are held together by electrostatic attraction (an ionic bond).