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