Download Section 2a: the periodic table The periodic table is a method of

Section 2a: the periodic table
2.1 understand the terms group and period
2.2 recall the positions of metals and non-metals in the Periodic Table
2.3 explain the classification of elements as metals or non-metals on the basis of their electrical
conductivity and the acid-base character of their oxides
2.4 understand why elements in the same group of the Periodic Table have similar chemical properties
2.5 recall the noble gases (Group 0) as a family of inert gases and explain their lack of reactivity in
terms of their electronic configurations
The periodic table is a method of classifying elements into groups and periods.
 group = vertical column of elements; within a group there are distinct chemical similarities but also
gradual changes in properties as we will see in groups 1 and 7.
 period = horizontal row of elements, from an alkali metal to noble gas.
Metals and non-metals
All elements in the periodic table are divided up into metals and non-metals. The metals are found to the
left and the middle whilst the non-metals on the right.
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metals
metals usually have high melting and boiling
points; they are all solids except mercury;
metals are malleable
metals are good conductors of heat and
electricity;
metals are usually shiny (most are also silvery);
metals are ductile
their oxides are basic (high pH)
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non-metals
variable melting and boiling points but usually
lower than in metals; most non-metals are
either solids or gases;
non-metals are brittle;
non-metals are poor conductors of heat and
electricity (except graphite);
non-metal oxides are acidic (low pH)
Group numbers
Relationship between electronic configuration of elements and their position in the Periodic Table:
 an element’s group number is the same as the number of valence electrons in its outer most shell.
 an element’s period number is the same as the number of shells which have electrons on them or the
number of the shell being filled .
The chemical properties of an element depend on the number of electrons in its most outer shell. As all
elements in the same group have the same number of valence electrons all elements in the same group
will have similar chemical properties. For instance all elements in group 1 have 1 electron in their last
shell and because of that are all very reactive.
Noble gases
The elements in the last group, group 0, are inert gases. They are unreactive because they have a full
outer shell (2 electrons in the case of helium and 8 electrons in the other noble gases) unlike the
elements in the other group.
Section 2a the periodic table
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