"Chemical Formula and Chemical Names of Ionic Compounds Writing Methodology and Worksheet"

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How to write the chemical formula and chemical names of ionic compounds
SNC2D1
Chemical formula:
 is a combination of symbols that represent a particular compound
 shows the combining ratio of atoms
Writing Chemical Formulas:
Example 1: what is the formula for the ionic compound formed by calcium and iodine?
STEP 1: Write the symbols, with the metal first.
Ca
I
STEP 2: Write the ionic charge above each symbol to indicate the stable ion that each
element forms.
2+
1-
Ca
I
STEP 3: Determine how many ions of each type you need so that the total ionic charge is
ZERO.
_____(+2) + ____ (-1) = 0
1 (+2) +
2 (-1) = 0
(+2) + (-2)
= 0
STEP 4: Write the formula using subscripts to indicate the number of ions of each type.
*NOTE: the subscript “1” is unnecessary because the symbol
CaI
2
itself represents ONE atom/ion
Writing chemical names:
Always remember, the metal keeps its name, and the non-metal needs the ending (suffix) to be
changed to “–ide”.
Using the example above, the chemical name of CaI
is Calcium iodide.
2
How to write the chemical formula and chemical names of ionic compounds
SNC2D1
Chemical formula:
 is a combination of symbols that represent a particular compound
 shows the combining ratio of atoms
Writing Chemical Formulas:
Example 1: what is the formula for the ionic compound formed by calcium and iodine?
STEP 1: Write the symbols, with the metal first.
Ca
I
STEP 2: Write the ionic charge above each symbol to indicate the stable ion that each
element forms.
2+
1-
Ca
I
STEP 3: Determine how many ions of each type you need so that the total ionic charge is
ZERO.
_____(+2) + ____ (-1) = 0
1 (+2) +
2 (-1) = 0
(+2) + (-2)
= 0
STEP 4: Write the formula using subscripts to indicate the number of ions of each type.
*NOTE: the subscript “1” is unnecessary because the symbol
CaI
2
itself represents ONE atom/ion
Writing chemical names:
Always remember, the metal keeps its name, and the non-metal needs the ending (suffix) to be
changed to “–ide”.
Using the example above, the chemical name of CaI
is Calcium iodide.
2
The Criss-Cross Method
-
An alternative way to find the chemical formulas (easier way) is to use the criss-cross rule
-
It replaces the steps 1, 3, 4 from above!
Using the example above, the compound formed by calcium and iodine:
STEP 1: write the ionic charges above the symbols.
STEP 2: criss-cross the numbers using them as subscripts.
Ca
2+
I
1-
Ca
I
1
2
STEP 3: get rid of any “1’s” as the subscript. And be sure to “simplify” any subscripts if
necessary.
Example 2: What is the chemical formula and name of the ionic compound formed by aluminum
and sulphur?
Method #1
Criss-Cross Method
Example 3: What is the chemical formula and name of the ionic compound formed by beryllium
and oxygen?
Method #1
Criss-Cross Method
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