What’s in a Compound?
Notes
compound – 2 or more atoms chemically bonded together
 Examples: H2O, NaCl, CO2
subscript - represents the number of atoms of an element
 If there is not a subscript, we understand it is 1.
 Only refers to the element before it.
 Example:
o O2 – 2 atoms of the element Oxygen
o O3 – 3 atoms of the element Oxygen
How do we read this?
H2 O
2 atoms of the element Hydrogen (H)
1 atom of the element Oxygen (O)
Lets Practice identifying atoms of the element! Complete the
chart below.
Compound
Common Name
NaCl
______ atoms of the element ____________
______ atoms of the element ____________
HCl
______ atoms of the element ____________
______ atoms of the element ____________
KNO3
______ atoms of the element ____________
______ atoms of the element ____________
______ atoms of the element ____________
NaHCO3
______ atoms of the element ____________
______ atoms of the element ____________
______ atoms of the element ____________
______ atoms of the element ____________
Lets Practice! How many atoms in a compound with a
coefficient?
Coefficient – represents the number of molecules of a compound
 If there is not a coefficient, we understand it to be 1.
 Only refers the compound behind it.
o Example:
 3HCl – 3 molecules of the compound hydrochloric acid
 2H2O – 2 molecules of the compound water
 The coefficient gets distributed and multiplied throughout the
compound to determine how many atoms of each element.
o Example:
 2H2O – The 2 gets distributed to the H and the O
 H = 4 atoms of the element hydrogen (2x2)
 O = 2 atoms of the element oxygen (2x1)
Let’s practice distributing!
Compound
How many atoms of each element?
______ atoms of the element ____________
2CO2
Carbon Dioxide
______ atoms of the element ____________
______ atoms of the element ____________
2H2SO4
(Sulfuric acid)
______ atoms of the element ____________
______ atoms of the element ____________
______ atoms of the element ____________
3H2O2
(Hydrogen Peroxide)
______ atoms of the element ____________
______ atoms of the element ____________
Now let’s put it all together!
Compound
What is in the compound?
_____ molecules of the compound _____________________
3HCl
(Hydrochloric
Acid)
is made up of
______ atoms of the element ____________
______ atoms of the element ____________
_____ molecules of the compound _____________________
2FeS2
(Fools Gold)
is made up of
______ atoms of the element ____________
______ atoms of the element ____________
_____ molecules of the compound _____________________
C6H12O6
(Glucose)
is made up of
______ atoms of the element ____________
______ atoms of the element ____________
______ atoms of the element ____________