1. The atomic number of an element is __________________________?

    Does this number ever change for atoms of the same element?

2. The atomic mass number of an element is ___________________________?

    If this number changes for an atom of a specific element you have an (ion, isotope)

    ___________________? Has the number of protons or neutrons changed?     
   

3. When an element exists in nature by itself, it must have a charge of ________?

    When that charge changes to become either plus or minus, you have changed the
    number of ___________________?

    If the charge becomes minus, you have (more or less) ____________ electrons than protons?

4. An atom has 7 protons, 7 electrons, and 8 neutrons. Fill in the blanks below for this atom:

       Atomic Number _______ Atomic mass: _______ Charge: ________

    This atom belongs to which element?

5. An ion of oxygen has a charge of –2. How many protons and electrons does the ion have?

6. An ion of potassium has a charge of +1. How many protons and electrons does this ion have?

7. The mineral fluorite is made of fluorine and calcium. Use the periodic table of the elements to determine what charge each of these elements will take in order to form a compound.

    Using this information, write a chemical formula for the compound, which makes up
    fluorite:

8. The element oxygen will always take a charge (valence) of –2 in naturally occurring rocks and minerals. The chemical formula for the compound, which makes up the mineral quartz, is SiO². What is the valence (charge) of silicon in this compound?

9. In some cases several atoms may combine to form a structure in which the electrical charge remains unbalanced. Such a structure is called a complex ion. One common complex ion is the carbonate ion, which consists of one carbon plus three oxygen atoms. Write the formula for the carbonate ion below, including the charge in the upper right:

10. An atom has 6 protons, 7 neutrons, and 6 electrons. Fill in the blanks below for this atom:

    Atomic number _____    Atomic mass number _____    Charge ______

     This atom belongs to which element?

11. A calcium ion has a charge of +2. How many protons and electrons does it have?

12. Sulfur is an element, which may remain neutral, take on a positive charge, or take on a negative charge.

    If no oxygen is present, sulfur will remain neutral or take on a negative charge. If it takes on a negative charge, it becomes a sulfide ion, and fills its outer electron orbital (shell) with additional electrons. Use the periodic table to determine what the charge should be on this ion:

    If oxygen is present, the sulfur will take a positive charge, and combine with the oxygen to produce a sulfate ion. If sulfur looses all of the electrons in its outer orbital (shell), what charge will it have?

    The sulfur will combine with 4 oxygen atoms. Each oxygen atom will take on a charge of –2. What is the total charge on all of the oxygen atoms put together?

    Now write the formula for the sulfate ion as a whole, with the net charge on the complex ion (radical) in the upper right: