A + B  AB Left-hand side is starting side reactants – A and B are reactants Right-hand side is ending side product – AB is product

Energy & Chemical Bonds Making a bond Releases energy! It’s exothermic!

A + B  AB + energy bond is formed: energy is released AB has less PE than A and B but AB is more stable than A and B

Equations for Ionic Bonding 2Na(s) + Cl 2 (g)  2NaCl(s) 2Na(s) + Cl 2 (g)  2NaCl(s) REACTANTS FORM PRODUCT –If product is formed, it’s more stable than reactants If it’s more stable, it has less energy

Stability vs. Energy endothermicendothermic process: – energy is absorbed –system goes from low to high energy –stability goes down exothermicexothermic process: –energy is released –system goes from high to low energy –stability goes up

The greater the energy released when the bond is formed, the more stable the bond is K + L  KL Joules Reaction2 B + C  BC Joules Reaction1 Which product is more stable, BC or KL?

Properties of Ionic Compounds High melting points Low vapor pressures Solids do not conduct electricity Molten state (liquid state) does conduct electricity Aqueous solutions conduct electricity Tend to be hard and brittle