Chemistry Formulas and Nomenclature
Formulas
In chemistry, a formula is a symbolic representation of a chemical compound. It provides information about the elements present in the compound and their relative proportions.
Types of Formulas
Empirical Formula: Represents the simplest whole-number ratio of atoms in a compound.
Molecular Formula: Shows the actual number of atoms of each element in a molecule of the compound.
Structural Formula: Depicts the arrangement of atoms and bonds within a molecule.
Nomenclature
Nomenclature is the system of naming chemical compounds. It helps in identifying and classifying compounds based on their composition and structure.
Types of Nomenclature
Ionic Compounds:
- Cations (positive ions) are named first, followed by anions (negative ions).
- Cations retain their element name (e.g., sodium, potassium).
- Anions change their ending to -ide (e.g., chloride, oxide).
- If the cation has multiple oxidation states, a Roman numeral is used in parentheses to indicate the charge (e.g., iron(II) oxide, iron(III) oxide).
Covalent Compounds:
- Prefixes are used to indicate the number of atoms of each element (e.g., mono-, di-, tri-, tetra-).
- The less electronegative element is named first.
- The more electronegative element is named second with an -ide ending.
Acids:
- Binary acids (contain only hydrogen and one other element) are named using the prefix "hydro-" and the suffix "-ic acid" (e.g., hydrochloric acid, hydrofluoric acid).
- Oxyacids (contain hydrogen, oxygen, and another element) are named based on the polyatomic ion present. The suffix "-ate" changes to "-ic acid" and "-ite" changes to "-ous acid" (e.g., sulfuric acid, sulfurous acid).
Common Formulas and Nomenclature
Ionic Compounds:
- NaCl - Sodium Chloride
- CaCO₃ - Calcium Carbonate
- Cu₂O - Copper(I) Oxide
- CuO - Copper(II) Oxide
Covalent Compounds:
- H₂O - Dihydrogen Monoxide
- CO₂ - Carbon Dioxide
- HCl - Hydrogen Chloride
Acids:
- HCl - Hydrochloric Acid
- H₂SO₄ - Sulfuric Acid
- H₂SO₃ - Sulfurous Acid
- HF - Hydrofluoric Acid
Additional Formulas
- Ideal Gas Law: PV = nRT
- Molar Mass: M = m/n
- Molar Volume: V = nRT/P
- Density: D = m/V
- Percent Composition: % composition = (mass element / mass molecule) x 100
