Download H 2 O

Content Assignment #1
Counting Atoms Notes
• Fold your paper in half – leave in notebook
• Write your notes on the left side and your
diagrams and examples on the right
• Count three lines from the bottom and
draw a line. You will write a “SUMMARY”
statement at the bottom.
• Remember to put your name, date, and
period AND assignment title at the top
right.
Leigh Miller,
Pillans M.S.
Content Assignment #1
Counting Atoms Notes
• What are subscripts?
• Subscripts are
numbers that
– Tell how many
atoms of that
element are in the
molecule
– Are written to the
RIGHT of the
element’s symbol
and slightly below
the line
SYMBOL
SUBSCRIPT
H2
O2
There are two hydrogen atoms and
two oxygen atoms shown here.
Content Assignment #1
Counting Atoms Notes
• What are subscripts?
• Subscripts are
numbers that
– Tell how many
atoms of that
element are in the
molecule
– Are written to the
RIGHT of the
element’s symbol
and slightly below
the line
SUBSCRIPT
H2O
There are two hydrogen atoms and
ONE oxygen atom shown here.
Content Assignment #1
Counting Atoms Notes
• What are subscripts?
• Subscripts are
numbers that
– Tell how many
atoms of that
element are in the
molecule
– Are written to the
RIGHT of the
element’s symbol
and slightly below
the line
SUBSCRIPT
H2O
CO2
There is ONE carbon atom and
TWO oxygen atoms shown here.
Content Assignment #1
Counting Atoms Notes
• What are
coefficients?
COEFFICIENT
• Coefficients are
numbers that
– Tell how many
molecules are
present
– Are written to the
LEFT of the
molecular formula
– Are MULTIPLIED
by all of the
There are two MOLECULES of
subscripts in the water and four molecules of
formula
carbon dioxide
2H2O
4CO2
Content Assignment #1
Counting Atoms Notes
• What are
coefficients?
COEFFICIENT
• Coefficients are
numbers that
– Tell how many
molecules are
present
– Are written to the
LEFT of the
molecular formula
– Are MULTIPLIED
by all of the
Now MULTIPLY 2 times 2 and 2
subscripts in the times 1.
formula
2H2O
Content Assignment #1
Counting Atoms Notes
• What are
coefficients?
COEFFICIENT
• Coefficients are
numbers that
– Tell how many
molecules are
present
– Are written to the
LEFT of the
molecular formula
– Are MULTIPLIED
by all of the
Now you have FOUR atoms of
subscripts in the hydrogen and TWO atoms of
formula
oxygen.
2H2O
Content Assignment #1
Counting Atoms Notes
• What are
coefficients?
• Coefficients are
numbers that
– Tell how many
molecules are
present
– Are written to the
LEFT of the
molecular formula
– Are MULTIPLIED
by all of the
subscripts in the
formula
COEFFICIENT
Now MULTIPLY 4 times
1 and 4 times 2.
4CO2
Content Assignment #1
Counting Atoms Notes
• What are
coefficients?
• Coefficients are
numbers that
– Tell how many
molecules are
present
– Are written to the
LEFT of the
molecular formula
– Are MULTIPLIED
by all of the
subscripts in the
formula
COEFFICIENT
Now you have FOUR
carbon atoms and
EIGHT oxygen atoms.
4CO2
Guided Practice: Keep your Science Notebook
open and copy the following chemical formulas.
Count the following atoms in each molecule.
Remember: Your test will be Friday, October 24.
1. Ag2S
_____Silver _____Sulfur
2. H2S
_____Hydrogen ______Sulfur
3. NaNO3 ___Sodium ___Nitrogen ___Oxygen
4. 2AgNO3 ___Silver ____Nitrogen ___Oxygen
5. 7Na3PO4 __Sodium ___Phosphorus__Oxygen
Homework: Count the atoms in
the following chemical formulas
1. NaCl
2. Cl2
3. MgCO3
4. 3HCl
5. MgCl2
6. H2CO3
7. 4ZnCl2
8. H2
Homework: Count the atoms in the following
chemical formulas
1. NaCl – 1 sodium; 1 chlorine
2. Cl2 – 2 chlorine atoms
3. MgCO3 – 1 magnesium; 1 carbon; 3
oxygen
4. 3HCl – 3 hydrogen; 3 chlorine
5. MgCl2 – 1 magnesium; 2 chlorine
6. H2CO3 – 2 hydrogen; 1 carbon; 3
oxygen
7. 4ZnCl2 – 4 Zinc; 8 chlorine
8. H2 – 2 hydrogen