We’ll show you another example where we name a compound with a multivalent
metal.
Name the compound Au2O.
Name: gold(II) ox ygen
Total
Positive
Charge
Au+
Au+
+2
O2–
–2
We’re asked to name the compound with the formula Au2O.
Total
Negative
Charge
Name the compound Au2O.
Name: gold(II) ox ygen
Total
Positive
Charge
We see that gold
Au+
Au+
+2
O2–
–2
Total
Negative
Charge
Name the compound Au2O.
Name: gold(II) ox ygen
Multivalent
+ Metal
Total
Positive
Charge
Au
Au+
+2
Has 2 charges so it’s a multivalent metal
O2–
–2
Total
Negative
Charge
Name the compound Au2O.
Name: gold(II) ox ygen
Multivalent
+ Metal
Total
Positive
Charge
Au
O2–
+
Au
A roman numeral
MUST
be used in–2
+2
the name.
Therefore, a roman numeral must be used in the name.
Total
Negative
Charge
Name the compound Au2O.
Name: gold(I) ox ygen
Total
Positive
Charge
Au+
Au+
+2
O2–
–2
We know the name of the metal is gold and it needs a roman numeral
Total
Negative
Charge
Name the compound Au2O.
Name: gold(I) ox ygen
Total
Positive
Charge
Au+
Au+
+2
O2–
And we know that the name of the non-metal is oxygen
–2
Total
Negative
Charge
Name the compound Au2O.
Name: gold(I) ox ygen
Au+
Au+
+2
O2–
The ending
needs to be
changed to “ide”
Total
Positive
Charge
–2
Total
Negative
Charge
But because this is a binary compound, the ending of the non-metal needs to be changed to ide.
Name the compound Au2O.
Name: gold(I) ox ygen
ide
Total
Positive
Charge
Au+
Au+
+2
So we replace “ygen” with “ide”
O2–
–2
Total
Negative
Charge
Name the compound Au2O.
Name: gold(I) ox ide
Total
Positive
Charge
And the name is gold oxide.
Au+
Au+
+2
O2–
–2
Total
Negative
Charge
Name the compound Au2O.
Name: gold(I) ox ide
Au+
Au+
+2
roman numeral
for charge on
one Au ion
?
Total
Positive?
Charge
O2–
–2
Total
Negative
Charge
In order to find the roman numeral that goes in here, we must find the charge on one gold ion,
is it positive 3 or positive 1?
Name the compound Au2O.
Name: gold(II) ox ide
Total
Positive
Charge
Au+
Au+
+2
O2–
–2
Total
Negative
Charge
Here’s how we do it. The formula tells us we have 2 gold ions and one oxide ion. We start with
the negative charge.
Name the compound Au2O.
Name: gold(II) ox ide
Total
Positive
Charge
Au+
Au+
+2
O2–
–2
The periodic table tells us the charge on one oxide ion is negative 2
Total
Negative
Charge
Name the compound Au2O.
Name: gold(II) ox ide
Total
Positive
Charge
Au+
Au+
+2
O2–
–2
Total
Negative
Charge
There is only one oxide ion, (click) so the total negative charge is negative 2.
Name the compound Au2O.
Name: gold(II) ox ide
Total
Positive
Charge
Au+
Au+
+2
O2–
Therefore the total positive charge must be positive 2
–2
Total
Negative
Charge
Name the compound Au2O.
Name: gold(II) ox ide
Total
Positive
Charge
Au+
Au+
+2
O2–
–2
Total
Negative
Charge
For the charges on 2 gold ions to add up to positive 2, each gold ion must have a charge of
(click), positive 1.
Name the compound Au2O.
Name: gold(I) ox ide
Total
Positive
Charge
Au+
Au+
+2
So we insert the roman numeral 1 in the brackets.
O2–
–2
Total
Negative
Charge
Name the compound Au2O.
Name: gold(I) ox ide
Total
Positive
Charge
Au+
Au+
+2
And the name of this compound is gold (I) oxide.
O2–
–2
Total
Negative
Charge