TYPES OF REACTIONS -- NOTES
Free elements (neutral elements which are not bonded to any other atoms) are written as either:
1) single atoms -- this is the case for almost all elements (e.g. Fe, Na, P, C) OR
2) diatoms -- Br2 I2 N2 Cl2 H2 O2 & F2 -- only these 7 elements are written this way
1) SYNTHESIS (SYN)
A) free element + free element

water

B)
metal oxide +
C)
metal oxide + carbon dioxide
D)
metal chloride
E)
nonmetal oxide + water
F)
metal oxide
+
+
binary compound

AX)


nonmetal oxide
metal carbonate
metal chlorate
oxyacid

salt (ternary ionic compound containing an oxyanion)
2) DECOMPOSITION (DEC)
A) binary compound  free element + free element
(AX
B)
metal hydroxide

metal oxide +
C)
metal carbonate

metal oxide + carbon dioxide
D)
metal chlorate
E)
oxyacid


metal hydroxide
oxygen

(A + X
metal chloride
nonmetal oxide

A + X)
water
+
oxygen
+ water
F) salt (ternary ionic compound containing an oxyanion)

metal oxide
+
nonmetal oxide
3) SINGLE REPLACEMENT (SR)
free element + compound 
new compound + new free element
(B + AX  BX + A)
If the free element can form a cation, it replaces a cation in the original compound.
If the free element can form an anion, it replaces an anion in the original compound.
Note: The free element on the reactant side must be more active than the element it is replacing!!
4) DOUBLE REPLACEMENT (DR)
compound + compound  new compound + new compound
(AX + BY  AY + BX)
Cations and anions trade “partners” to form two new compounds.
Note: These reactions will not actually take place unless the product includes an insoluble ionic
compound, or a molecular compound (i.e. if both products are soluble ionic compounds,
then no reaction takes place).
NOTES: For both SR and DR reactions, you must use your knowledge of the ions to predict
appropriate product formulas. Also, when water appears in SR and DR reactions, it is
helpful to write water as HOH not H2O
5) COMBUSTION (COMB)
Hydrocarbon + oxygen
 carbon dioxide + water
(CxHyOz + O2
 CO2 + H2O)
The hydrocarbon consists of carbon and hydrogen, and may also include oxygen (e.g. an alcohol).
Oxygen always appears as a reactant. Carbon dioxide and water always appear as products.