5: Chemical Nomenclature
- Page ID
- 289370
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There are many substances that exist as two or more atoms connected together so strongly that they behave as a single particle. These multi-atom combinations are called molecules. Molecules are the smallest part of a substance that have the physical and chemical properties of that substance. In some respects, a molecule is similar to an atom. A molecule, however, is composed of more than one atom.
- 5.1: Elements Combine to Form Compounds
- A compound is a substance that contains two or more elements chemically combined in a fixed proportion. Because the elements are chemically combined, they cannot be separated using physical means. In addition, the properties of the compound (both physical and chemical) are radically different than the constituent elements that make up these compounds.
- 5.2: Chemical Formulas
- A chemical formula is an expression that shows the elements in a compound and the relative proportions of those elements. A molecular formula is a chemical formula of a molecular compound that shows the kinds and numbers of atoms present in a molecule of the compound. An empirical formula is a formula that shows the elements in a compound in their lowest whole-number ratio.
- 5.3: A Closer Look at Elements and Compounds
- Most elements exist with individual atoms as their basic unit. However, there are many substances that exist as two or more atoms connected together so strongly that they behave as a single particle. These multi-atom combinations are called molecules. If the atoms are all the same element, it is known as a molecular element. If the atoms are from different elements, it is either an ionic compound or a molecular compound.
- 5.4: Classification of Compounds
- The primary function of chemical nomenclature is to ensure that a spoken or written chemical name leaves no ambiguity concerning which chemical compound the name refers to: each chemical name should refer to a single substance. A less important aim is to ensure that each substance has a single name, although a limited number of alternative names is acceptable in some cases. Preferably, the name also conveys some information about the structure or chemistry of a compound.
- 5.5: Binary Ionic Compounds
- Formulas for ionic compounds contain the symbols and number of each atom present in a compound in the lowest whole number ratio. Ionic compounds are named by stating the cation first, followed by the anion. Positive and negative charges must balance.
- 5.6: Ions With Variable Charges
- Some cations have multiple charges and are named accordingly with the use of Roman numerals in parentheses to indicate the particular charge of the cation.
- 5.7: Ionic Compounds Containing Polyatomic Ions
- Polyatomic ions are groups of atoms bonded together with an overall charge. They can be used to form ionic compounds in the same manner as individual ions. Polyatomic ions have characteristic formulas, charges, and names which should be memorized for ease in relating names and formulas to each other.
- 5.8: Binary Molecular Compounds
- Molecular compounds are inorganic compounds that take the form of discrete molecules. Because they are not held together by electrostatic attractions, the ratios of the atoms to each other can vary. Thus, the number of each element in the compound must be indicated using Greek prefixes.
- 5.9: Acids
- An acid can be defined in several ways. The most straightforward definition is that an acid is a molecular compound that contains one or more hydrogen atoms and produces hydrogen cations (H⁺) when dissolved in water. Acids are named based on the anion formed when the hydrogen ion is removed.
- 5.10: Nomenclature Summary
- Brief overview of chemical nomenclature.
This page is shared under a CK-12 license and was authored, remixed, and/or curated by Melissa Alviar-Agnew, Henry Agnew, Vicki MacMurdo (Anoka-Ramsey Community College), and Lance S. Lund (Anoka-Ramsey Community College).
