1. In this example, we’ll show you how to write the formula for an ionic compound with a multivalent metal.

2. A multivalent metal is a metal which can form more than one ion. Each ion it forms has a different positive charge. Multivalent Metal - A metal which can form more than one ion, each with a different charge

3. On the periodic table you’re given, multivalent metals are the ones which have more than one charge in the top right corner. They are shown in this diagram. Multivalent Metals

4. Here, we’ve included the two horizontal rows at the bottom of the periodic table, as many of these are multivalent. Multivalent Metals

5. In this example, we’re asked to write the formula for the compound copper (II) chloride. +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride.

6. We find copper on the periodic table. It is a metal and it can form an ion with either a positive 2 charge, or a positive 1 charge. Write the formula for the compound copper(II) chloride.

7. The element we use for chloride is chlorine. It’s ion, the chloride ion has a charge of negative 1. Write the formula for the compound copper(II) chloride.

8. The periodic table tells us that copper can form either a positive 2 ion or a positive 1 ion. Cu 2+ Cl – +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride.

9. How do we know what the charge will be on the ion?? Cu 2+ Cl – +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride. ?

10. Names of compounds with multivalent metals always have a roman numeral in brackets right after the name of the metal. Cu 2+ Cl – +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride. ? roman numeral -means the charge on the ion

11. The roman numeral simply means the charge on the ion that is used in the compound. Cu 2+ Cl – +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride. ? roman numeral -means the charge on the ion

12. So a roman numeral of 2 tells us the copper ion that’s used has a charge of positive 2. Cu 2+ Cl – +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride. ?

13. So the copper ion in this compound is Cu 2 plus Cu 2+ Cl – +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride.

14. The chloride ion has only one possible charge, and that is negative 1. Cu 2+ Cl – +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride.

15. If we have one copper II ion and one chloride ion Cu 2+ Cl – +2–1 CuCl 2 Cl – Write the formula for the compound copper(II) chloride. Total Positive Charge Total Negative Charge

16. The positive and negative charges are NOT balanced. They don’t add up to zero Cu 2+ Cl – +2–1 CuCl 2 Cl – Write the formula for the compound copper(II) chloride. Total Positive Charge Total Negative Charge These DO NOT add up to zero

17. To make the charges balance, we add another chloride ion (click) Cu 2+ Cl – +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride. Total Positive Charge

18. The total negative charge is now negative 2. Cu 2+ Cl – +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride. Total Positive Charge Total Negative Charge

19. Now the positive and negative charges are balanced. They add up to zero Cu 2+ Cl – +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride. Total Positive Charge Total Negative Charge NOW these add up to zero

20. There is one copper ion for every two chloride ions, Cu 2+ Cl – +2–2 Cl – Write the formula for the compound copper(II) chloride.

21. So the formula is CuCl 2 Cu 2+ Cl – +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride.

22. We have now answered the question. The formula for copper (II) chloride is CuCl 2. Cu 2+ Cl – +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride. Formula:

23. Notice that the final formula has no charges and no roman numerals in it. In simple ionic compounds, roman numerals are used only in names, not in formulas. Cu 2+ Cl – +2–2 CuCl 2 Cl – Write the formula for the compound copper(II) chloride. Formula: No charges! No roman numerals!