Page 75 - Chemistry_Form_2

Chemistry
for Secondary Schools

Example 3.9
What is the name of the compound with the formula FeCl ?
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Solution

The total charge of the molecule is zero and Cl has a negative charge.
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(i) Let x be the charge of Fe
(ii) 1(x) + 3(–1) = 0
(iii) x = +3

(iv) So, the Fe is in the +3 oxidation state. Write the name ‘iron’ and place III
in brackets beside it.
(v) Use the name ‘chlorine’ but change the last three letters to “ide”: So the
name is iron(III) chloride.

Example 3.10

What is the name of the compound with the formula CuS?

Solution
(i) Let x be the charge of Cu.

(ii) Sulfur has a charge of –2.
(iii) 1(x) + 1(–2) = 0

x = +2 for Cu
(iv) Write the name copper and place II in brackets beside it.

(v) Use the name sulfur but change the last two letters to ide. The name of the
compound is copper(II) sulfide.

Other examples of the names of binary ionic compounds are:

(a) MgO is named magnesium oxide.

(b) AlCl is named aluminium chloride.
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(c) MnO is named manganese(IV) oxide.
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Note: Manganese can have more than one charge, but each oxygen ion has a
charge of –2. For the compound to be neutral, Mn must have a charge
of +4.

68 Student’s Book Form Two

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