1. In this example, we’ll show you how correctly name a compound that contains a multivalent metal.

2. The method of naming compounds with multivalent metals uses a roman numeral. For example, titanium has two charges shown on the top right, so it is (click) a multivalent metal A multivalent metal

3. The naming method for multivalent metals we’re going to outline must be used here. The naming method for multivalent metals must be used here so that a roman numeral can be found to specify the charge that is being used. A multivalent metal

4. So that a roman numeral can be found which will specify which ion of titanium is being used, the ion with a positive 3 charge, or the ion with a positive 4 charge. The naming method for multivalent metals must be used here so that a roman numeral can be found to specify the charge that is being used. A multivalent metal

5. The metal magnesium has only one charge shown on the top right of its box, so it (click) is a metal with only one charge. A multivalent metal A metal with only 1 charge The naming method for multivalent metals must be used here so that a roman numeral can be found to specify the charge that is being used.

6. The simple method you learned before without roman numerals must be used for compounds of metals like magnesium that only have one charge A multivalent metal A metal with only 1 charge The naming method for multivalent metals must be used here so that a roman numeral can be found to specify the charge that is being used. The simple naming method without roman numerals must be used here. The metal has only 1 possible charge, so a roman numeral is not needed

7. The metal has only one possible charge, so a roman numeral is NOT needed to specify which charge is being used. A multivalent metal A metal with only 1 charge The naming method for multivalent metals must be used here so that a roman numeral can be found to specify the charge that is being used. The simple naming method without roman numerals must be used here. The metal has only 1 possible charge, so a roman numeral is not needed

8. If student uses a roman numeral in the name for a compound with a metal that has only one charge (click), the answer will be marked wrong. A multivalent metal A metal with only 1 charge The naming method for multivalent metals must be used here so that a roman numeral can be found to specify the charge that is being used. The simple naming method without roman numerals must be used here. The metal has only 1 possible charge, so a roman numeral is not needed No roman numerals!

9. Multivalent metals are easy to find, they have more than one charge shown in the top right corner of their box. They are shaded here, so you can see where they are. Multivalent Metals Use roman numerals

10. Roman numerals must always be used in the names of compounds of these metals Multivalent Metals Use roman numerals

11. Notice that these multivalent metals are all found in the center and bottom sections of the periodic table. None are found on the far left of the table. Multivalent Metals Use roman numerals

12. Metals with only one possible charge are shaded in green here. Metals with Only One Charge

13. Do NOT use roman numerals in the names of compounds of these metals Metals with Only One Charge Do NOT use roman numerals!

14. Its helpful to remember that among others, all of the metals in groups 1 and 2 on the periodic table have only one possible charge each. Metals with Only One Charge Do NOT use roman numerals! Group 1Group 2

15. So roman numerals are never used in names of compounds of these metals. Metals with Only One Charge Do NOT use roman numerals! Group 1Group 2

16. Now we’ll use an example to show you the method we use to name multivalent metal compounds. We are asked to name the compound with the formula Cu 3 As 2. Cu 2+ As 3– +6–6 Name: copper(II) arsenide Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+

17. We check the metal copper on the periodic table. We see there are two charges written on the top right, (click) so copper is multivalent. Cu 2+ As 3– +6–6 Name: copper(II) arsenide Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ Multivalent

18. That means a roman numeral MUST be used in the name. Cu 2+ As 3– +6–6 Name: copper(II) arsenide Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ Multivalent A roman numeral MUST be used in the name.

19. We’ll start by naming the elements Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

20. We know the metal name is copper. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

21. And the non-metal is arsenic Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ic

22. But because this is a binary compound, the ending of the non-metal must be changed to –ide. It now ends in “ic” Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ic The “ic” ending needs to be changed to “ide”

23. So we replace “ic” with “ide” (click) Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ic ide

24. Giving us the name copper arsenide. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

25. But remember, copper is a multivalent metal. It has more than one possible charge. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide ? ?

26. We need to specify the charge on each copper ion by writing a roman numeral in brackets right after the name copper. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide A roman numeral ? ?

27. We find the charge on each copper ion in this compound by finding what positive charge is needed to balance the total negative charge. Let’s see how that’s done… Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide ? ? We find the charge on each copper ion in this compound by finding what positive charge is needed to balance the total negative charge.

28. The formula tells us we have three copper ions Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

29. For every 2 arsenide ions. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

30. The periodic table tells us that each arsenide ion has a charge of negative 3. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

31. At this point, we don’t know whether the copper ions have a charge of positive 2 or positive 1. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide ? ? ?

32. What we do is calculate the total negative charge. It is negative 3 plus negative 3.. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide ? ? ?

33. Which is equal to negative 6. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide ? ? ?

34. Charges must be balanced, (click) so this means that Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide ? ? ?

35. The total positive charge is positive 6. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide ? ? ?

36. So the total charge on the three copper ions is positive 6. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide ? ? ? The total charge on 3 copper ions is +6

37. This would be true if each copper ion has a charge of positive 2. Three times positive 2 is equal to positive 6. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide The total charge on 3 copper ions is +6

38. So now we know that the charge on one copper ion is positive 2. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

39. Therefore, we can put the roman numeral 2 in the bracket after copper. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

40. So the name is copper (II) arsenide Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

41. To quickly review the process, the formula tells us we have 3 copper ions and 2 arsenide ions. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

42. The periodic table tells us the charge on each arsenide ion is negative 3 Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

43. So the total negative charge is negative 6 Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

44. Therefore the total positive charge must be positive 6. Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

45. Because there are 3 copper ions and the total positive charge is positive 6 (click), the charge on each copper ion must be positive 2 Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

46. Therefore the name is copper II arsenide, where the roman numeral 2 is written in the bracket Cu 2+ As 3– +6–6 Name: copper(II) arsen Name the compound Cu 3 As 2. Total Positive Charge Total Negative Charge Cu 2+ As 3– Cu 2+ ide

47. The final answer to the question is the correct name for this compound is copper(II) arsenide. Name: copper(II) arsen Name the compound Cu 3 As 2. ide Final Answer