Covalent Bonds (for AP120 & BIO120)*

1. Covalent Bonds(for AP120 & BIO120)* * From a chemistry standpoint, some of this is incorrect or a gross over-simplification, but it gives you the right idea and serves our purpose

2. Covalent Bonds

3. When electron pairs are shared, both atoms get to “count” the electrons as if it was part of their own outer shell. One, two, or three electron pairs can be shared (this forms single, double, and triple covalent bonds respectively

4. Formation of Covalent Bonds

5. Covalent bonds form when…. • two or more atoms come into close proximity • once in close proximity they begin to share electron pairs (i.e., electrons move around both nuclei) • the shared electrons count towards “filling” the outer energy shell • covalent bonds are an example of the sharing of electrons to fill outer energy (electron shells)

6. Covalent bond formation

7. Covalent bond formation

8. Covalent bond formation Two atoms held together by a covalent bond (sharing of electrons)

9. Covalent Bonds • When one pair of electrons are shared a single covalent bond is formed • If two pairs of electrons are shared they for a double covalent bond • Three shared pairs of electrons makes a triple bond • The more electrons that are shared the stronger the bond is (i.e., triple bonds are stronger than doubles, doubles stronger than singles)

10. Polar and Non-polar bonds • If the electrons in a covalent bond are shared equally between the atoms the result is a non-polar bond. • If the electrons are not equally shared, and they spend more time around one of the atom’s nuclei, then the result is a polar bond. • A polar bond results in charged regions within a molecule that overall, is neutral

11. THE END* • Consult your lecture notes for characteristics of covalent bonds and covalently bound molecules.