2 Chapter 6 • organising elements Organising elements

Properties and structure
6.2
How do we organise elements?
Remember and understand
1 What is the name given to the following
features of the periodic table?
a a horizontal row
b a vertical column
c the set of ten groups from group 3 to
group 12
2 State the group number of the following sets
of elements:
a alkaline earth elements
b halogens
c noble gases
d alkali metals
3 What is a valence shell?
4 State the features that elements in the same
group have in common.
5 State the features that elements in the same
period have in common.
6 Suggest why transition metals are much more
widely used than the alkali metals.
7 Give explanations for the following.
a Hydrogen was placed in the same group as a
set of metals, even though it is a non-metal.
b Helium was placed in the same group as
the noble gases, even though its uncharged
atoms have a different number of electrons
in the valence shell to those of the other
group members.
8 An inert substance is one that will not react
with any other substance. Originally, group
18 elements were known as the ‘inert gases’.
Suggest why the name was changed to
‘noble gases’.
Apply
9 Only two elements are liquids at room
temperature—bromine and mercury. Bromine is
a non-metal and mercury is a metal. Describe
how these two liquids are likely to appear and
behave differently from each other.
Analyse and evaluate
10 a some sodium metal was introduced into a
sealed jar containing chlorine gas. The metal
and gas reacted to produce sodium chloride,
which is table salt. Would you expect this
reaction to need heat to get it going or would
you expect it to produce heat? Would you
expect it to be a mild reaction or a more violent
one? Justify your answers.
Properties and structure
b What two elements would you expect to
react together in the most violent way?
Justify your answer.
11 Before the 1980s, the groups of the periodic
table were numbered with Roman numerals.
Some scientists prefer this version because
the uncharged atoms of the elements in
group III (now 13) have three electrons in
their valence shell, those in group IV (now 14)
have four electrons in their valence shell and
so on. Examine how the groups of transition
metals were numbered in the old way. Which
numbering system do you think is the most
helpful? How can you deduce the number of
electrons in the valence shell from the new
group number?
12 The elements are ordered according to their atomic number. Groupings reflect the properties of the elements.
Properties can change when elements combine. How might the location of an element on the periodic table
give you an indication of the likely combinations of elements and the potential property changes?
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Chapter 6 • organising elements
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