How can the polarity of a covalent bond be determined?
1 Answer
The polarity of a covalent bond can be determined by determining the difference in electronegativity (
The difference in electronegativities (
- If the ΔEN is less than 0.5, then the bond is nonpolar covalent.
- If the ΔEN is between 0.5 and 1.6 (some use 1.7), the bond is considered polar covalent
- If the ΔEN is greater than 2.0, then the bond is ionic.
- If the ΔEN is between 1.6 and 2.0, and a metal is involved, then the bond is considered ionic. If only nonmetals are involved, the bond is considered polar covalent.
*Note that absolute values are used; there are no negative differences in electronegativity.
**A note about Rule 4: Some websites and textbooks consider a
(Source: http://www.chemteam.info/Bonding/Electroneg-Bond-Polarity.html)
Example
Determine the
-
silicon (Si) and phosphorus (P): EN of Si = 1.90, EN of P = 2.19
#Delta"EN"# = 1.90 - 2.19 = 0.29, therefore the bond is nonpolar covalent. -
carbon (C) and oxygen (O): EN of C = 2.55, EN of O = 3.44
#Delta"EN"# = 2.55 - 3.44 = 0.89, therefore the bond is polar covalent. -
sodium (Na) and chlorine (Cl): EN of Na = 0.93, EN of Cl = 3.16
#Delta"EN"# = 0.93 - 3.16 = 2.23, therefore the bond is ionic.