Writing Formulas - Naming Compounds

 This program demonstrates how to write chemical formulas   as well as naming inorganic compounds and acids.

 Please read each section carefully.  You might wish to take notes.

 Note that the oxidation state for atoms has the sign and then number, while the charge on a polyatomic ion has the number and then sign.

 Main Menu

1] - Writing chemical formulas

2] - Naming compounds

3] - Acid nomenclature  

4] - Practice Problems

5] - Side A  versus  Side B   practice problems

6] - Common Ions

7] - Practice Quiz 1       Practice Quiz 2

 

Writing Chemical Formulas

1)  For 2 elements having different oxidation states:

    a) write the symbols, listing the element with a positive oxidation state first (this will be a metal or something acting like a metal)

    example:         Ca  F

    b) above each symbol, place the oxidation state of that element

    example:         +2  -1
                               Ca  F

    c) subscripts must be written below and to the right of the symbols so that the sum of electrons lost will be equal to the number gained. These subscripts must be in the lowest whole number ratio.

       In our example the calcium atom will lose 2 outershell (valence) electrons

            --->      CaF₂          

2)  For 2 elements having the same oxidation states:

    a) subscripts will not be needed for ionically bonded compounds

    b) molecular weights are used to determine subscripts for covalently bonded compounds

    c) remember never to use `1' as a subscript

    example:         +2  -2
                              Ca  O      --->   CaO

    Here each atom of calcium lost two electrons and each oxygen atom gained two electrons

    example:         +2          1-
                               Ca  ClO₃     --->   Ca(ClO₃)₂           

   example:          +1         1-
                                K   ClO₃     --->   KClO₃

    Now we need to look at lots of examples.  

 Problem # 1:    potassium + oxygen

    +1   -2     --->   K₂O            2 potassium atoms are needed to supply
      K    O                                 1 electron each to the oxygen

 

Problem # 2:   beryllium + iodine

     +2   -1     --->   BeI₂           the two iodide atoms take one electron
      Be   I                                  each from the beryllium atom

 

Problem # 3:    calcium + carbon

    +2   -4       ---->    Ca₂C        2 calcium atoms give up 2 electrons each
    Ca   C                                    (4 electrons total)

 

Problem # 4:    magnesium  + nitrogen

    +2     -3       ---->    Mg₃N₂       3 magnesium atoms give up 6 electrons,
    Mg   N                                        2 nitrogen atoms take in 6 electrons

 

Problem # 5:    calcium + bromate

     +2           1-       ---->    Ca(BrO₃)₂        each calcium loses 2 electrons,
     Ca   BrO₃                                               each of 2 bromate ions gains 1

             

Problem # 6:    sodium phosphate

    +1          3-       ---->    Na₃PO₄         3 sodium atoms donate an electron
    Na   PO₄                                            to the single phosphate ion

          

Problem # 7:    aluminum sulfate

    +3         2-       ---->    Al₂(SO₄)₃        magic number = 6 electrons
     Al   SO₄                                              transferred from Al to sulfates

         

Problem # 8:    ammonium hydroxide

     1+      1-       ---->    NH₄OH         each ammonium loses 1 electron to
   NH₄   OH                                         each hydroxide ion

     

Problem # 9:    lithium oxide

    +1   -2       ---->    Li₂O          2 lithium atoms are needed to give
      Li   O                                    up the 2 total electrons needed

   

Problem # 10:    strontium chlorate

    -2          1-       ---->    Sr(ClO₃)₂          2 chlorate ions accept 1 electron
    Sr   ClO₃                                               each from the strontium atom