Principles of Chemistry
7 marks · EasyStudents are discussing the behaviour of elements in the Periodic Table.
Define the term 'atom' and give an example.
Explain why elements in the same group (excluding Group 0) of the Periodic Table show similar chemical properties.
Helium and neon do not form any compounds. Using atomic structure, explain why the Group 0 elements are inert.
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(a) An atom is the smallest part of an element that can still be recognized as that element. Example: a helium atom.
(b) Elements in the same group have the same number of electrons in their outer shell. This causes them to react in similar ways.
(c) Group 0 elements (noble gases) have full outer shells of electrons, so they are stable and do not tend to gain, lose, or share electrons. This explains why they are chemically unreactive (inert).
Common mistakes: Not linking group similarity to outer electrons; Confusing atom with molecule
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Marking points
B1 (a) · 1 mark · Correct definition of atom as smallest part of an element retaining its identity.
B2 (a) · 1 mark · Correct example (e.g., helium atom, oxygen atom)
B3 (b) · 1 mark · States that group members have the same number of outer shell electrons.
B4 (b) · 1 mark · Links this to similar chemical properties or reactions.
B5 (c) · 1 mark · States noble gases have full outer shells (or stable arrangements).
B6 (c) · 1 mark · Links full shell to lack of tendency to gain/lose/share electrons.
B7 (c) · 1 mark · Correctly explains chemical inertness as a result.
Worked solution
a) An atom is the smallest part of an element that can still be recognized as that element. Example: a helium atom.
b) Elements in the same group have the same number of outer-shell electrons. Since chemical reactions depend on outer electrons, these elements react in similar ways.
c) Group 0 elements have full outer electron shells, making their electron arrangement stable. This means they do not want to gain, lose, or share electrons, so they are inert and do not react or form compounds.