Chemical Elements & Compounds

Outline of Topics

This section introduces the foundational concepts of chemical compounds, their classification, and the principles underlying their formulas and nomenclature. The main topics include:

• Types of chemical compounds & their formulas

• The mole concept & chemical compounds

• Composition of chemical compounds

• Oxidation states

• Naming simple inorganic compounds

• Names & formulas of inorganic compounds

Types of Chemical Compounds & Their Formulas

Definition and General Features

A chemical is defined as a distinct compound or element. A key characteristic of all compounds is that they are composed of two or more elements chemically combined in fixed proportions.

• Simple chemical compounds (cpds): These are compounds with relatively few atoms, such as CO2, CO, NH3, and H2O.

• Complex compounds: These contain more atoms and may have more intricate structures, such as Vitamin C (ascorbic acid) and aspirin (acetylsalicylic acid).

Example: Vitamin C (ascorbic acid) is a complex organic compound with the formula C6H8O6.

Classification of Chemical Compounds

Chemical compounds can be broadly classified into two main types based on their bonding and structure:

• Molecular Compounds: Composed of discrete units called molecules. These molecules consist of nonmetals bonded together by covalent bonds.

• Ionic Compounds: Made up of positive ions (cations, typically metals that lose electrons) and negative ions (anions, typically nonmetals that gain electrons). These ions are held together by electrostatic forces.

Example: Sodium chloride (NaCl) is an ionic compound, while water (H2O) is a molecular compound.

Empirical and Molecular Formulas

The empirical formula (EF) of a compound is the simplest formula that shows the elements present and their relative whole-number ratios. The molecular formula gives the actual number of atoms of each element in a molecule of the compound.

• Empirical Formula Example: is the empirical formula for diphosphorus pentoxide.

• Molecular Formula Example: is the molecular formula for the same compound.

Key Point: The empirical formula is always the simplest ratio, while the molecular formula may be a multiple of the empirical formula.

Summary Table: Types of Chemical Compounds

Additional info: The distinction between empirical and molecular formulas is crucial for understanding chemical composition and stoichiometry. Empirical formulas are especially useful in analytical chemistry and when determining formulas from experimental data.