Naming Simple Compounds and Writing Formulas
Chemical language
Formulas
A chemical formula shows which elements are present and how many atoms of each are in a substance. For example, means two hydrogen atoms and one oxygen atom.
Reading formulas
The small number written below and to the right of an element symbol is called a subscript. It tells how many atoms of that element are present.
Writing a simple ionic formula
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1
Write the ion charges.
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2
Choose numbers so total charge is zero.
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3
Use the smallest whole-number ratio.
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4
Write the formula without charges.
Common formula symbols
What does the subscript in mean?
The 2 in means there are two hydrogen atoms.
Correct answer: Two hydrogen atoms
What does a chemical formula tell you?
Formulas summarize composition in a compact way.
Correct answer: Which elements are present and how many atoms of each
Which formula represents carbon dioxide?
Carbon dioxide contains one carbon atom and two oxygen atoms.
Correct answer: CO2