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Names and Formulas of Bases

Role of cation and anion in naming compounds

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Names and Formulas of Bases

Making soap requires a base, lye

Credit: Unknown
Source: http://commons.wikimedia.org/wiki/File:Zeepzieden.jpg
License: CC BY-NC 3.0

What different things are these workers doing to make soap?

Soap making has a long history.  Until recently, soap was made using animal fats and lye from wood ashes.  The lye served as a base to break down the fats and help form the soap.  Needless to say, unless the soap was washed to remove the lye, it was very harsh on the skin.  Many families would make their own soap by boiling the lye and fat in a large kettle over an open fire, a long and hot task.


The simplest way to define a base is an ionic compound that produces hydroxide ions when dissolved in water.  One of the most commonly used bases is sodium hydroxide, illustrated below.

Picture and structure of sodium hydroxide

Credit: (A) Martin Walker (Wikimedia: Walkerma); (B) Ben Mills (Wikimedia: Benjah-bmm27)
Source: (A) http://commons.wikimedia.org/wiki/File:SodiumHydroxide.jpg; (B) http://commons.wikimedia.org/wiki/File:Sodium-hydroxide-crystal-3D-vdW.png
License: CC BY-NC 3.0

(A) Sodium hydroxide, a base, is a solid that is typically produced as small white pellets. (B) The structure of sodium hydroxide is an extended three-dimensional network. The purple spheres are the sodium ions (Na+). The red and white spheres are oxygen and hydrogen atoms respectively, which are bonded together to form hydroxide ions (OH).[Figure2]

Names and Formulas of Bases

There is no special system for naming bases.  Since they all contain the OH- anion, names of bases end in hydroxide.  The cation is simply named first.  Some examples of names and formulas for bases are shown in the Table below.

Formula Name
NaOH sodium hydroxide
Ca(OH)2 calcium hydroxide
NH4OH ammonium hydroxide

Notice that because bases are ionic compounds, the number of hydroxides in the formula does not affect the name.  The compound must be neutral, so the charges of the ions are balanced just as for other ionic compounds.  Sodium ion (Na+) requires one OH- ion to balance the charge, so the formula is NaOH.  Calcium ion (Ca2+) requires two OH- ions to balance the charge, so the formula is Ca(OH)2.  Hydroxide ion is a polyatomic ion and must be put in parentheses when there are more than on in a formula.


  • Bases are ionic compounds that produce hydroxide ions when dissolved in water.
  • The cation is named first followed by “hydroxide.”


  1. What is a base?
  2. What is the charge on the hydroxide anion?
  3. Name the following bases:
    1. LiOH
    2. Mg(OH)2
    3. Fe(OH)3
  4. Write the formulas for the following bases:
    1. nickel (II) hydroxide
    2. aluminum hydroxide
    3. silver hydroxide

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Image Attributions

  1. [1]^ Credit: Unknown; Source: http://commons.wikimedia.org/wiki/File:Zeepzieden.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: (A) Martin Walker (Wikimedia: Walkerma); (B) Ben Mills (Wikimedia: Benjah-bmm27); Source: (A) http://commons.wikimedia.org/wiki/File:SodiumHydroxide.jpg; (B) http://commons.wikimedia.org/wiki/File:Sodium-hydroxide-crystal-3D-vdW.png; License: CC BY-NC 3.0

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