Synthesis reactions involve the combination of smaller atoms and/or molecules into larger molecules:

A + B AB

Decomposition reactions involve the splitting of a large molecule into elements or smaller molecules:

AB A + B

Single Displacement reactions involve an element and a compound as reactants. One element displaces or replaces another element form a compound.

magnesium+silver nitrate silver +magnesium nitrateMg + AgNO3 Ag + Mg(NO3)2

Mg + 2AgNO3 2Ag + Mg(NO3)2

Single displacement reactions have the general formula:

Z + AB ZB + A Or

Y + AB AY + B**In the first case, the metal Z has taken the place of element A. In the

second case, the nonmetal Y has taken the place of element B

Double Displacement reactions occurs when elements in different compounds displace each other or exchange places

lead nitrate + potassium iodide lead iodide + potassium nitrate

Pb(NO3) + KI PbI2 + KNO3

Pb(NO3)2 + 2KI PbI2 + 2KNO3

Double displacement reactions have the general formula:

AB + XY AY + XB

**Where A and X are metallic elements and B and Y are nonmetallic elements.