Ionic Compounds

1
Ionic Compounds

• Atoms are rarely found in nature in their pure
  state. Most often they are combined with other
  elements in compounds.
• Two major types of compounds we will study are
  molecular and ionic compounds.
• These two major groups of compounds are different
  by the way they combine.
• Metals and nonmetals combine to form binary ionic
  compounds. Nonmetals combine with other
  nonmetals to form compounds and polyatomic ions.

2
Forming Ions

• Ions are elements which have gained or lost one
  or more electrons.
• Elements gain or lose electrons to achieve
  greater stability.
• Many atoms gain or lose electrons to become
  isoelectronic with the noble gases.
• Electrons are gained or lost from the outermost
  electron shell.
• A general rule is Last one in is the first one
  out.

3
Forming Ions

• If atoms lose electrons they become positively
  charged because they have more protons than
  electrons.
• These ions are called Cations.
• The metals of the periodic table form cations.
• Lithium loses its outer electron and becomes
  isoelectronic with the noble gas helium.
• The lithium ion is then written as Li
• An ion and its element have different physical
  and chemical properties.

4
Forming Ions

• If atoms gains electrons they become negatively
  charged because they have more electrons than
  protons.
• These ions are called Anions.
• The nonmetals of the periodic table form anions.
• Fluorine gains an outer electron and becomes
  isoelectronic with the noble gas Neon.
• The fluorine ion is then written as F-
• An ion and its element have different physical
  and chemical properties.

5
Forming Ions

• Many metals and nonmetals form predictable ions.
• All alkali metals, with hydrogen, form 1
  cations.
• All alkaline earth metals form 2 cations.
• Aluminum forms a 3 cation, Al3.
• All halogens for -1 anions.
• Column 16 nonmetals form -2 anions.
• Column 15 nonmetals form -3 anions.
• Carbon does not form an ion, nor do the
  metalloids with the exception of arsenic, As3-.

6
5.1 Ions

• Transition and post transition metals form
  cations that are not as predictable as column I
  II elements.
• Transition metals may form more than one type of
  cation.
• Most transition metals form ions to achieve
  stability in some other way than being
  isoelectronic with the noble gases.

7

• Losing electrons is also called oxidation.
• The chart below shows the possible oxidation
  states of the transition metals.
• Notice that most of them form multiple ions.