2.4: ions and ionic compounds

ions

• ion: an atom or group of atoms with a charge
  • charged atoms are monatomic ions whereas charged groups of atoms are polyatomic ions
• cation: a positively charged ion
  • formed when an atom loses an electron or electrons
• anion: negatively charged ion
  • formed when an atom gains an electron or electrons
• ionic compounds are held together by the attraction between the oppositely-charged ions
• ionic solids are often called salts
• atoms gain or lose electrons to become more stable
• elements seek to achieve the electron configuration of the closest noble gas to them on the periodic table
• when they gain or lose electrons, atoms become charged (ions)

compounds and bonding

• compound: a pure substance that contains two or more elements
• the type of elements present dictate the type of compound and bonding of the substance
• types of compounds
  • ionic compounds
  • formed between a metal and a nonmetal
  • have ionic bonds (electrons are transferred from the metal atom to the nonmetal atom)
  • electrostatic attraction holds ions together
  • form formula units
  • molecular compounds
  • formed between two nonmetals
  • have covalent bonds (electrons are shared by the nonmetal atoms)
  • form molecules