Trends of the Periodic Table
Chapter 4 – VCE Chemistry
Metallic and Non-metallic
Character
• Elements can be
compared in terms of
metallic or non-metallic
character.
• Metals usually have;
Lustre, conductivity of
heat and electricity,
malleable and ductility.
• Non-metals generally do
not have the above
properties.
Metalloids
• Metalloids posses properties
of both metals and non
metals.
• The are found in the
‘staircase’ between the
metals and the non-metals.
Examples; Silicon
Properties
• Semi conductor of electricity
• Solid at room temperature
• Dark grey colour
• Melting point 1410oC
Silicon
Hydrogen – A Special Case
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Although it is found in group 1,
hydrogen is not a metal.
It is located in group 1 due it having 1
shell and 1 valence electron.
However, recent research has found
that Hydrogen can act like a group 1
metal under extremely high pressure
conditions.
Questions 5.1
• Complete questions 1-5 on P. 93 of
Nelson VCE Chemistry.
Classes of Compounds
• Compounds are formed
when two or more elements
join together to make a new
substance.
• The millions of different
compounds can be
classified based on their
chemical bonding type.
• Types of bonds include;
Metallic, ionic and covalent.
• Chemical bonds will be
studied later in Unit One.
Oxides of the Elements
• Most elements combine with
oxygen to form oxides.
• These compounds are called
binary compounds due to
having two elements present.
• Oxides usually have acid-base
properties.
• Metals – Ionic compounds
(Base oxides)
• Non-metals – Covalent
molecular compounds (Acidic
oxides).
• Group 18, the noble gases, do
not combine with oxygen.
Other Compounds
• Metals usually combine with non-metals to form ionic compounds
(salts).
• They can also be mixed together to form alloys.
• Non-metals combine with each other to form covalent molecules
and compounds.
• Carbon and silicon can form large lattice structures.
• Polymers, long chained molecules, are also made from non-metals.
Questions 5.2
• Complete questions 1-5 on P. 99100 of Nelson VCE Chemistry.
Reactive and Un-reactive
Elements – Non-metals
• Elements differ in terms of their
chemical reactivity with other
substances.
• Some elements can only be
stored and handled by trained
professionals due to their
reactivity.
• The least reactive elements are
the noble gases.
• The most reactive element is
Fluorine. It readily reacts with
most elements to form fluorides.
• Fluorine gas is extremely
dangerous to handle.
• Non-metals close to Fluorine are
also reactive.
Reactivity of Metals
• The most reactive metal is
Caesium. It has to be stored in
an argon filled container to
prevent it spontaneously
combusting in air.
• Reactivity increases down the
group. Francium would
theoretically be even more
reactive than Caesium!
• The least reactive metal is gold.
This is why it one of the few
elements that are naturally
found in elemental form.
Explaining Trends in
Reactivity
• When a reactive metal and nonmetal come in contact, a violent
reaction occurs.
• Heat and light energy are rapidly
released.
• For example a violent reaction
occurs between sodium and
chlorine to form sodium chloride.
• Why are group 1 and 17 the most
reactive elements?
• Why are group 18 unreactive?
• The next few slides give
explanations for these trends
Explaining the Trends of
Reactivity
First Ionisation Energies
• The amount of energy required to remove 1 electron from an uncharged
element (Forming an ion) is called the first ionisation energy.
• Ionisation energy increases across a period.
• Metals readily lose electrons, whereas non-metals resist.
• Ionisation energy decreases down a group. Therefore caesium will form
ions more easily than lithium.
Atomic Radius
• The size of the atom also
determines its reactivity.
• The larger the atom, the
more readily it will form an
ion. This is because the
outermost electrons are
found further from the
nucleus in the heavier
elements compared to the
lighter elements.
• Metals are also called
reductants as they lose
electrons. Caesium is
therefore a stronger
reductant than sodium.
Electronegativity
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Electronegativity is the electron drawing
power of an element.
The greater the number, more readily the
atom will attract electrons into its structure.
The scale used is called the Pauling scale
of electronegativities.
Noble gases do not have electronegativity
values.
Electronegativity increases across a period
and up a group. This is due to the atomic
radius of the atoms.
Metals have low electronegative values
due to the fact that they want to lose
electrons – not gain them.
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Non-metals want to gain electrons
to fill their outer shell.
Fluorine, the most reactive element,
has the highest electronegative
value of 3.98.
Summary- Trends in Groups
Summary-Trends in Periods
Comparing Group 1 and 17
Summary of Trends
Questions 5.3
• Complete questions 1-5 on P. 1067 of Nelson VCE Chemistry.
Review Questions
• Complete questions 1-9 on P. 109110 of Nelson VCE Chemistry.