Counting Atoms Worksheet
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1Counting Atoms Worksheet
Chemical formulas consist of element symbols and numbers that indicate how many atoms of
each element are present. For example in the molecule C
H
, there are 3 Carbon atoms and 8
3
8
Hydrogen atoms. In CO
, there is 1 Carbon atom(we don’t write the
in the chemical formula)
2
1
and 2 Oxygen atoms. For an example of when parenthesis are involved, please see Fig. 1 for
the pictorial representation of H(CO
)
. As you can see there is 1 Hydrogen atom, 2 Carbon
3
2
atoms, and 6 Oxygen atoms.
H
O
C
O
O
C
O
Fig. 1
O
O
O
When there is a number in front of the compound, that indicates how many molecules of a
compound there is. For example, 3H
O means there are 3 molecules of H
O. See Fig. 2 for the
2
2
pictorial representation of 3H
O. As you can see, there are 3 Oxygen atoms and 6 oxygen
2
atoms.
O
O
O
Fig. 2
H
H
H
H
H
H
Please complete the following charts.
Na
CO
3BaCl
Ca
(PO
)
2
3
2
3
4
2
Type of Atom
# of Atoms
Type of Atom
# of Atoms Type of Atom
# of Atoms
Total
Total
Total
NH
C
H
O
2(NH
)
Cr
O
4Al
(CO
)
4
2
3
2
4
2
2
7
2
3
3
Type of Atom
# of Atoms
Type of Atom
# of Atoms Type of Atom
# of Atoms
Total
Total
Total
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