1. Unit 2: Biochemistry
2.2 Chemical Bonding

2. Chemical Bond A force that holds atoms together in a compound.
They do this by gaining, losing, or sharing electrons

3. Covalent bond
Covalent bond: the attraction that forms between atoms when they share electrons.
Forms a neutral compound called a molecule
Usually occurs between nonmetals
Single covalent bonds – sharing of 2 electrons (one from each atom in the bond)
Multiple bonds – sharing of more than one electron by each atom

4. Single Bonds

5. Multiple Bonds

6. Ionic Bond
Ionic Bond: the force of attraction between the opposite charges of ions, electrons are transferred.
Occurs when electrons are lost or gained (transferred between atoms)
Usually formed between metals and nonmetals
Ex. Salt NaCl

7. Ionic Bond Na… Na+ Loses a electron, Becomes positive Cl.... Cl-
Gains an electron,
Becomes a negative

9. Hydrogen Bond
Hydrogen Bond: a hydrogen atom bonded to one molecule is attracted to the slightly negative area (often N or O) of another molecule.
Very weak individual bond.
Can be a “strong” force if there are many H bonds.

10. Hydrogen Bonds

11. Polar/Nonpolar Molecules
Polar Covalent Molecules: molecule with a slightly positive and a slightly negative end although the overall molecule is neutral
Ex. H2O
Nonpolar Molecules: a molecule in which the electrons are shared evenly (does not have oppositely charged ends)
2 molecules of the same atom or symmetric molecules
Ex. CCl4 N2

12. Polar Covalent
Ex. HCl

13. Bonding Analogy
Create a picture analogy to represent the three different kinds of bonds. An analogy is a comparison of two things.
Key Ideas:
Covalent: atoms share electrons.
Ionic: atoms transfer electrons from one atom to another.
Hydrogen: opposite poles (positive end and negative end) of molecules attract.