Polar and Nonpolar Covalent Bonds

1. Polar and Nonpolar Covalent Bonds • Covalent bonding involves sharing electrons between atoms. • Nonpolar covalent bond – equal sharing of electrons between two atoms. • Both atoms have same attraction for shared pair. • Example: H – H

2. Polar covalent bond – unequal sharing of electrons between atoms. • One atom has greater attraction for shared pair. (Tug – of – War) • Example: H – Cl • This creates partial (d) charges on each atom in the bond.

3. The atom that has a greater attraction for shared electrons takes on a partialnegativecharge and the atom with a weaker attraction takes on a partial positivecharge. • How can you determine which atom has greater attraction for electrons?

4. Electronegativity • Electronegativity – measures the ability of an atom to attract electrons from an another atom. • Scale in which atom is assigned a number between 0 and 4. • Higher the number, the stronger the attraction for electrons. • Atom with highest electronegativity is fluorine. Fluorine’s value is 4.

5. Electronegativity Values

6. Electronegativity Trends • Metals tend to have lowelectronegativities; while nonmetalstend to have highelectronegativities. • Electronegativitiesdecreaseas you go down a group. • Electronegativities generally increase as you go across a period until you reach the noble gases.

7. Can use the difference in electronegativities between two atoms to predict the type of bond formed between the atoms.

8. Sample Problem: • Use electronegativities to determine the type of bond that will form. If the bond is polar, decide which atom is partially negative and which is slightly positive. (a) C and S (b) Na and O (c) P and Cl