MOLECULES AND IONS

• Molecules


  Made up of atoms that are chemically bonded together. They can be a combination of atoms of the same element or different elements. Molecules can be diatomic or polyatomic.
• Diatomic molecules


  Contain only two atoms and normally occur in nature.
• Homonuclear diatomic molecules


  • H2, Cl2, Br2
• Heteronuclear diatomic molecules


  • HCl, NO, HF
• Polyatomic molecule


  Contains three or more atoms
• Polyatomic molecules


  • O3, CO2, C2H2
• Ions


  Atoms or molecules that have a charge. Ions with positive charge are called cations, while ions with negative charge are called anions.
• Determine whether the following are atoms, molecules, or ions: N, N2, NO3, O2, O2-, CO, K+, Ar, HPO4 2-, H2O2
• Structural formula


  A representation of a compound using the symbol of the elements to indicate how the atoms are arranged and bonded chemically.
• Molecular formula


  Shows the atoms present in a compound, as well as the number of atoms per element present in it.
• Empirical formula


  Shows the simplest form of the atomic ratio in a chemical compound.
• Ball-and-stick model


  Depicts a 3-dimensional representation of the atoms of a compound and the bonds between them.
• Space-filling model


  Depicts the atoms of a compound using spheres that are joined together, approximating the proportionate sizes of the atoms.
• Ionic compound


  A neutrally-charged compound that contains a cation and an anion. Cations are usually metallic, while anions are usually nonmetallic.
• Naming ionic compounds (cation has only one oxidation state)

  1. Name the metal

  2. If the anion is monoatomic, add the suffix -ide to the root of the name of the nonmetal

  3. If the anion is polyatomic, use the name of the anion
• Naming ionic compounds (cation has more than one oxidation state)

  1. Name the metal

  2. Indicate the charge of the metal cation using Roman numerals and enclose it in parentheses or use suffixes -ous and -ic
• Naming molecular compounds


  1. Use prefixes for both elements in the compound to indicate the number of atoms for each element present

  2. Add the suffix -ide to the root of the name of the second element
• Naming molecular compounds


  • SF6: Sulfur hexafluoride
  • P2S3: Diphosphorus trisulfide
  • CF4: Carbon tetrafluoride
  • P2O5: Diphosphorus pentoxide
• Give the chemical name or formula, whichever applies, of the following compounds: MgO, SO3, Fe(OH)3, SeCl6, Cu(HCO3)2, Nitrogen trihydride, Potassium permanganate, Dinitrogen tetroxide, Ammonium nitrate, Phosphorus pentachloride