C3.01 The Periodic Table -
classifying elements
● Mendeleev 1869: Table based on atomic masses. His success was for
leaving gaps for possible elements still to be discovered and predicting the
properties of elements not yet discovered.
● The main distinction in the table is between metals and non-metals
(completely different)
● Non-metals are grouped into the top right-hand region of the table
● WIth the Periodic Table we can know which type of element is the one to
be considered so we may be able to predict some of its properties.
Metals and non-metals
● 94 natural occurring elements
● 70 of them can be classified as metals
● Together they form groups of elements whose structures are held together
by a particular type of bonding between the atoms.
● Metals have a number of physical properties that are broadly the same for
all of them.
● Chemical properties of metals and non-metals are also very different as is
the type of bonding present in their compounds.
● The Periodic Table does not list substances such as steel, bronze and brass
because they aren't elements, they are alloys.
Metals Non-metals
Usually solids at room temperature Solids or gases at room temperature
(mercury is a liquid). (bromine is a liquid).
High melting and boiling points. Low melting and boiling points.
Usually hard and dense. Non-metals are softer than metals.
Their densities are low
Good electricity conductors. Poor electricity conductors (insulators).
Good heat conductors. Poor thermal conductors
They are malleable and ductile. Brittle when solid
, Are grey in colour (except for gold and Vary in colour.
copper). Dull surface when solid.
Are sonorous. Are not sonorous.
● Non-metals are a less uniform group of elements, showing a much wider
range of properties.
● The change from metallic to non-metallic properties is not as clear as
suggested by dividing them into two regions.
● Elements close to the line show properties that lie between these extremes
known as metalloids or semi-metals.
● Metalloids have some of the properties of metals and others that are more
characteristic of non-metals.
● There are 8 elements considered metalloids
● Often look like metals but are brittle like non-metals.
● They are neither conductors nor insulators but make excellent
semiconductors
Groups and periods in the periodic table
● The periodic table allows us to make more useful subdivisions of elements.
● The elements present in Groups I to VIII of the table are known as the main-
group elements.
● These vertical groups show how elements within the same group have
similar chemical and physical properties.
● Some groups have particular names as well as numbers.
● Between Groups II and III is a block of metals known as the transition
elements.
● The noble gases, in group VIII/0, on the right hand side of the table are the
least reactive elements.
● The halogens, located next to the noble gases in group VII and the alkali
metals in group I are the most reactive elements.
● The more unreactive elements are in the centre of the table.
Electron arrangement and the Periodic Table
● Elements in the same group have the same number of outer electrons
● As you move across a period in the table, a shell of electrons is being filled.
classifying elements
● Mendeleev 1869: Table based on atomic masses. His success was for
leaving gaps for possible elements still to be discovered and predicting the
properties of elements not yet discovered.
● The main distinction in the table is between metals and non-metals
(completely different)
● Non-metals are grouped into the top right-hand region of the table
● WIth the Periodic Table we can know which type of element is the one to
be considered so we may be able to predict some of its properties.
Metals and non-metals
● 94 natural occurring elements
● 70 of them can be classified as metals
● Together they form groups of elements whose structures are held together
by a particular type of bonding between the atoms.
● Metals have a number of physical properties that are broadly the same for
all of them.
● Chemical properties of metals and non-metals are also very different as is
the type of bonding present in their compounds.
● The Periodic Table does not list substances such as steel, bronze and brass
because they aren't elements, they are alloys.
Metals Non-metals
Usually solids at room temperature Solids or gases at room temperature
(mercury is a liquid). (bromine is a liquid).
High melting and boiling points. Low melting and boiling points.
Usually hard and dense. Non-metals are softer than metals.
Their densities are low
Good electricity conductors. Poor electricity conductors (insulators).
Good heat conductors. Poor thermal conductors
They are malleable and ductile. Brittle when solid
, Are grey in colour (except for gold and Vary in colour.
copper). Dull surface when solid.
Are sonorous. Are not sonorous.
● Non-metals are a less uniform group of elements, showing a much wider
range of properties.
● The change from metallic to non-metallic properties is not as clear as
suggested by dividing them into two regions.
● Elements close to the line show properties that lie between these extremes
known as metalloids or semi-metals.
● Metalloids have some of the properties of metals and others that are more
characteristic of non-metals.
● There are 8 elements considered metalloids
● Often look like metals but are brittle like non-metals.
● They are neither conductors nor insulators but make excellent
semiconductors
Groups and periods in the periodic table
● The periodic table allows us to make more useful subdivisions of elements.
● The elements present in Groups I to VIII of the table are known as the main-
group elements.
● These vertical groups show how elements within the same group have
similar chemical and physical properties.
● Some groups have particular names as well as numbers.
● Between Groups II and III is a block of metals known as the transition
elements.
● The noble gases, in group VIII/0, on the right hand side of the table are the
least reactive elements.
● The halogens, located next to the noble gases in group VII and the alkali
metals in group I are the most reactive elements.
● The more unreactive elements are in the centre of the table.
Electron arrangement and the Periodic Table
● Elements in the same group have the same number of outer electrons
● As you move across a period in the table, a shell of electrons is being filled.
