Page 74 - Chemistry_Form_2

Chemistry
for Secondary Schools

Task 3.6

Use online resources such as Chemguide to explore detailed explanations and
examples of the nomenclature of various binary inorganic compounds. Summarise
the key rules for naming these compounds, including binary ionic compounds,
FOR ONLINE READING ONLY
covalent compounds and any exceptions.

Nomenclature of binary ionic compounds
Ionic compounds are formed when a metal combines with a non-metal. The
following are the steps considered when naming binary ionic compounds:

1. Name the metallic ion that appears first in the formula using the name of the
element itself.

2. The second part of the formula which is usually an anion in the compound
will end with a suffix “ide”. For example, oxygen becomes oxide, hydrogen
becomes hydride and chlorine becomes chloride.
Note:
(a) Some metals always have fixed charges when they form ions, that is,

(i) Group I metals have a charge of +1.
(ii) Group II metals have a charge of +2.

(iii) Group III metals have a charge of +3.
(iv) Silver (Ag) has a charge of +1.

(v) Zinc (Zn) has a charge of +2.

(b) Other metals are multivalent and can thus form more than one ion. For
example; iron (Fe) is bivalent; it has valencies of 2 and 3, copper (Cu) is
also bivalent; it has valencies of 1 and 2. Compounds formed from these
metals must be distinguished by stating which valency has been used in
the compound. The valency of the respective metal is indicated by capital
Roman numbers in parentheses (brackets), for example cobalt(II) chloride,
copper(II) oxide and iron(III) oxide. In chemical nomenclature, it is common
practice not to leave a space between the name of a metal and its oxidation
state written in Roman numbers.

Student’s Book Form Two 67

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CHEMISTRY FORM TWO NEW 2025 DUMMY.indd 67