Practice!

Sample Problem

 is an atom of element X

 is an atom of element Y

 is an atom of element Z

Using the above information, how many X, Y, and Z molecules are in the compound shown below?

Number of atoms of X

Number of atoms of Y

Number of atoms of Z

Solution

There are 5 green circles and 3 red circles so there are 5 atoms of element Z and 3 atoms of element X. Because there are no blue circles, the number of atoms of element Y is 0.