Unit 2: Biochemistry 2.2 Chemical Bonding

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

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

Single Bonds

Multiple Bonds

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

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

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.

Hydrogen Bonds

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

Polar Covalent Ex. HCl

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.