Periodic Table

The Periodic Table

The periodic table is used as a method of classifying and predicting the properties of elements.

Periodic Trends

Elements become more non-metallic across a period. Elements near the bottom left corner of the table are the most metallic while elements near the top right corner are the least metallic.

An element's group number is equal to the number of electrons in its outer shell (valence electrons). For example, oxygen is in group 6 and has 6 valence electrons.

Group Properties

Group 1

This is a collection of soft metals that react with water to produce an alkali and hydrogen.

Going down a group:

• melting point decreases
• reactivity increases

Group 7

This is a collection of diatomic nonmetals and are also known as halogens.

Going down a group:

• boiling point decreases
• reactivity decreases
• colour darkens

Transition Elements

This is a collection of metals that:

• have high melting points
• have high densities
• form coloured compounds
• often act as catalysts

Noble Gases

This is a collection of unreactive monoatomic gases that belong to group 8. These gases are unreactive because their valence (outer) shell is full. This means they rarely form compounds.