Some Types ofChemical Reactions

THE PERIODIC TABLE: METALS, NONMETALS, AND METALLOIDS

In 1869, the Russian chemist Dmitri Mendeleev (1834–1907) and the German chemist Lothar Meyer (1830–1895) independently published arrangements of known elements that are much like the periodic table in use today. Mendeleev’s classification was based primarily on chemical properties of the elements, whereas Meyer’s classification was based largely on physical properties. The tabulations were surprisingly similar. Both emphasized the periodicity, or regular periodic repetition, of properties with increasing atomic weight.

Some Physical Properties of Metals and Nonmetals

Some Chemical Properties of Metals and Nonmetals

General trends in metallic character

OXIDATION–REDUCTION REACTIONS

• 4Fe(s)+ 3O2(g) → 2Fe2O3(s)

COMBINATION REACTIONS

• Reactions in which two or more substances combine to form a compound are called combination reactions.

• Element + Element → Compound– Metal + Nonmetal → Binary Ionic Compound– Nonmetal + Nonmetal → Binary Covalent Compound– Compound + Element → Compound– Compound + Compound → Compound

DECOMPOSITION REACTIONS

• Decomposition reactions are those in which a compound decomposes to produce (1) two elements, (2) one or more elements and one or more compounds, or (3) two or more compounds.

Compound → Element + Element

Compound → Compound + Element

Compound → Compound + Compound

DISPLACEMENT REACTIONS

• Reactions in which one element displaces another from a compound are called displacement reactions.

(a) Bromine, Br2, in water ( paleorange) is poured into an aqueoussolution of NaI, the top layer in the cylinder.

(b) Br2 displaces I from solution and forms solid iodine, I2.The I2 dissolves in water to give abrown solution but is more soluble in many organic liquids ( purple bottom layer)

METATHESIS REACTIONS

• In many reactions between two compounds in aqueous solution, the positive and negative ions appear to “change partners” to form two new compounds, with no change in oxidation numbers. Such reactions are called metathesis reactions.

Acid–Base (Neutralization) Reactions: Formation of a Nonelectrolyte

Precipitation Reactions

Gas-Formation Reactions