1. QX₂. (Make it neutral; balance the charges.)

2. Q₃Z₂. (Same idea. This is about as complex a case there is for common ions. Sometimes, the idea of "least common multiplier" is helpful. If you use that, be sure to simplify. Example, calcium oxide is properly written CaO, not Ca₂O₂.)

3. 2+ (It is in group 2A. This idea works well near the edges of the PT.)

4. a. CO₃^2- (This is one you are supposed to know. But let's assume you don't. You know K⁺, from the PT, and you know the formula is neutral. Therefore, by logic, carbonate must be the other end of the molecule, and must be 2-.)
b. Na₂CO₃ (Na is 1+, like K.)
c. CaCO₃ (See #3.)
d. FeCO₃ [Iron(II) means Fe²⁺.]
e. Fe₂(CO₃)₃ (Fe³⁺; also see #2. Note how the final 3 means 3 of what is in the parentheses.)