Writing Chemical Formulas

Writing Chemical Formulas

By NAUDIA LAWRENCE

Learnong Target:

1. I can write a Chemical Formula given the Chemical name of a compound.

At the end of the lesson you should be able to write a chemical Formula when you are given the name of a compound

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In this Lesson

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After bonding together, there is no charge. The compound is neutral.

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The chages cancel each other

​Two ions combine to form a neutral compound.

Sodium Chloride is an example

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Before we learn the steps for writing a formula lets review how to find the charge or oxidation number of an element

​Some text here about the topic of discussion.

Lets Review Key concepts

Multiple Choice

What is the oxidation number of the elements in Group 1 of the periodic table

• -1

• +1

• -2

• -3

Multiple Choice

What is the oxidation number of the ION in Group 15 of the periodic table

• +2

• +4

• -2

• -3

Multiple Choice

What is the oxidation number of the elements in Group 13 of the periodic table

• -2

• +3

• 0

• -3

Multiple Choice

What is the oxidation number of Neon in Group 18 of the periodic table

• -2

• 0

• +3

• -3

Multiple Choice

Some ions have more than one elements and cannot be found on the periodic table. Using your reference tables determine the chatge of a Cyanide (CN) ion

• +4

• -2

• +1

• -1

Table E shows the IONS that have more than 1 Elements in them.

The CYANIDE ION has the elements Carbon and Nitrogen in it.

​We muust also know how to write formulas for Trabsition metals

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Transition Metals

​What do the numbers in parentheses mean in the chemical names above

Turn and talk

The roman numeral in paretheses tells us which ion is present in that compound

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Iron Has 2 Oxidation Numbers

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​What do the numbers in parentheses mean in the chemical names above

Turn and talk

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Multiple Choice

What is the oxidation number of Nickel in Nickel (III) Chloride?

• +1

• +6

• +7

• +4

Multiple Choice

What is the oxidation number of Chromium in Chromium (VI) Oxide?

• +1

• +6

• +7

• +4

Multiple Choice

What is the oxidation number of Manganese in Manganese (IV) Oxide?

• +1

• +6

• +7

• +4

Writing Chemical Formulas

I will Now model the steps for writing Ionic Compounds while you ffollow along.

I will then give you notes on these step to use in your examples

First, Write the symbol for the Metal and the Non-metal. The Non Metal ALWAYS ends with "IDE"

Write the Formula for Magnesium Choride.

Determine the charges on the Metal and the non-metal. If there is a Roman numeral after the metal that is the number of the charge

Criss-Cross the charges. The number from the charge of the metal goed below the non-metal and the number of the charge of thenon-metal goes below the metal as a subscript.

Final Formula

​Write the Symbols and charge
Criss cross charges
Do not write 1_s
Do not write the same numbers

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Lithium
Oxide

​Write the Symbols and charge
Criss cross charges
Do not write 1_s
Do not write the same numbers

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Aluminum
Oxide

​Write the Symbols and charge
Criss cross charges
Do not write 1_s
Do not write the same numbers

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Sodium Chloride

​Write the Symbols and charge
Criss cross charges
Do not write 1_s
Do not write the same numbers

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Calcium Oxide

​Write the Symbols and charge
Criss cross charges
Do not write 1_s
Do not write the same numbers

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Potassium Nitrate

​Write the Symbols and charge
Criss cross charges
Do not write 1_s
Do not write the same numbers

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Potassium Sulphate

​Write the Symbols and charge
Criss cross charges
Do not write 1_s
Do not write the same numbers

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Potassium Sulphate

​Write the Symbols and charge
Criss cross charges
Do not write 1_s
Do not write the same numbers

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Calcium Phosphate

Lets write the steps to Writing ionic compounds in our Notebooks. We will use Magnesium chloride as our example

Write the symbol for the Metal and the Non-metal

Step 1

STEP 2

Determine the charges on the Metal and the non-metal. If there is a Roman numeral after the metal that is the number of the charge

Criss-Cross the charges. The number from the charge of the metal goed below the non-metal and the number of the charge of thenon-metal goes below the metal as a subscript. The + and - dont move

Step 3

Step 4: If the number is a one (1) don't write it. If the two numbers are the same don't write them

For polyatomic ions follow the same rules but only criss cross the number in the charge and write the ion the same as it appears on on TABLE E
Use Parentheses to separate the numbers in the chrge and the ion

Independently answer the questions on your worksheet

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