Periodic Table - Arrangement of Elements

Objective

Explain how the position of an element in the Periodic Table can be used to predict its properties.

Understanding the Periodic Table

The Periodic Table organizes elements based on their atomic number, electron configuration, and recurring chemical properties. The arrangement is not random; it reflects underlying patterns in the electronic structure of atoms.

Periods and Groups

Periods: The horizontal rows in the Periodic Table are called periods. Elements within the same period have the same number of electron shells.

Groups: The vertical columns in the Periodic Table are called groups. Elements within the same group have the same number of valence electrons and therefore similar chemical properties.

Groups 1 and 2: Metals

Group 1 (Alkali Metals) and Group 2 (Alkaline Earth Metals) are metals. They are highly reactive and readily lose one or two electrons to form positive ions.

• Alkali Metals (Group 1):
• Highly reactive with water.
• React vigorously with halogens.
• Have low melting and boiling points.
• Increase in reactivity down the group.
• Alkaline Earth Metals (Group 2):
• Reactive with water, but less so than alkali metals.
• React with halogens.
• Have higher melting and boiling points than alkali metals.
• Increase in reactivity down the group.

Groups 3 to 12: Transition Metals

These are metals with variable valency. They often form coloured compounds and are good conductors of electricity and heat.

Their properties are less predictable than alkali and alkaline earth metals.

Groups 13 to 18: Non-metals

These elements generally do not readily lose or gain electrons. They can be solids, liquids, or gases at room temperature.

• Halogens (Group 17):
• Highly reactive non-metals.
• React with metals to form salts.
• Reactivity decreases down the group.
• Noble Gases (Group 18):
• Very unreactive (inert).
• Have full outer electron shells.
• Used in lighting and other applications.

Metals vs. Non-metals

Property	Metals	Non-metals
Appearance	Usually shiny	Dull
Conductivity	Good conductors of heat and electricity	Poor conductors of heat and electricity
Malleability	Malleable (can be hammered into sheets)	Brittle (easily breakable)
Ductility	Ductile (can be drawn into wires)	Not ductile
Reactivity	Generally reactive (lose electrons)	Generally unreactive (gain electrons)

Trends in Properties

Atomic Radius: Increases down a group and decreases across a period.

Ionisation Energy: Decreases down a group and increases across a period.

Electronegativity: Decreases down a group and increases across a period.

Predicting Properties

By understanding the position of an element in the Periodic Table, we can predict its properties. For example:

• Elements in the same group have similar chemical properties.
• Elements in the same period have similar physical properties.
• The position of an element indicates its tendency to lose or gain electrons.