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Chemistry
for Secondary Schools
The elements in Group I (except hydrogen) are called, alkali metals because
they react with water to form an alkaline solution. These elements are lithium
(Li), sodium (Na), and potassium (K), each having one electron in the outermost
shell. Note that, even though hydrogen is placed in Group I, it is not an alkali
metal. It carries some properties which are similar to those of Group I elements
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and others which are similar to those of Group VII elements. Therefore, some
periodic tables such as Newlands’ place it in the same group as Group VII
elements, such as fluorine and chlorine.
Group II elements are called alkaline earth metals. They have properties similar to
those of Group I elements, but they are less reactive. Group II elements also form
alkaline solutions when they react with water. Their oxides are stable, insoluble
solids that historically were referred to as "earths,” giving the term earth
Group VII elements are called halogens (’salt formers’ in Greek) because they
react with metals to form compounds called salts. Group VIII elements are
usually referred to as Group 0 elements. They are called noble gases and all
their shells are completely filled with electrons. They were formerly called inert
gases because they do not readily react to form compounds. The elements in the
block between Group II and Group III are transition elements. These elements
have high densities and melting points, form coloured compounds, and often act
as catalysts. Metalloid elements such as boron (B), silicon (Si), and germanium
(Ge) exhibit both metallic and non-metallic properties.
Metals Non-metals
Groups
I II III IV V VI VII VIII/0
Alkali metals earth Alkaline metals Transition Halogens Noble gases (Inert gases)
metals
Key: Metalloids
Figure 2.1: Sketch of the periodic table showing groups of elements
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