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Atoms, Ions, and Molecules



Atoms, ions, and molecules are the building blocks of all matter. Scientists use different systems and models to represent the way atoms come together to form molecules. For example, chemical formulas are a set of chemical symbols showing the elements and their fixed ratios in a compound. Molecular models illustrate the way atoms are arranged in space and the way they are bonded. Scientists also have other methods to distinguish between atoms, ions, and molecules. For example, isomers are molecules that have the same chemical formula but different arrangements of atoms. Oxidation states are hypothetical numbers assigned to atoms, ions, or polyatomic ions. They indicate the electric charge that an atom would have if it gained or lost electrons. Inorganic compounds can be divided into covalent compounds, ionic compounds, and acids. There are different naming conventions for each group.

At A Glance

  • Molecular formulas and empirical formulas provide information about molecules.
  • Each molecular model has advantages and disadvantages. Molecular models provide information about the type and number of atoms found in a molecule and some models show molecule shape and bond types.
  • Structural and spatial isomers are variations of molecules.
  • Oxidation states can be used to predict the compounds formed by a reaction.
  • Established naming conventions can be used to name ionic and molecular compounds.
  • Ionic compounds are typically metals bonded with nonmetals, and the cation and anion that form the compound provide the basis for their nomenclature.
  • Ionic compounds are those with ionic bonds and are named according to the identity of the cation.
  • Binary covalent molecules are named similarly to ionic compounds, with the addition of Greek prefixes indicating the number of atoms.
  • An acid releases hydrogen ions (H+) when dissolved in water. An acid consists of an anion bonded to hydrogen, with its naming conventions following naming conventions of anions.