Periodic Trends (Cambridge (CIE) IGCSE Combined Science): Revision Note

The metallic character of elements

• The metallic character of the elements:

  • Decreases as you move across a period on the Periodic Table, from left to right

  • Increases as you move down a Group

• Across a period:

  • Atoms become less likely to lose electrons and more likely to gain or share electrons

  • So, metallic character decreases

• Metals occur on the left-hand side of the Periodic Table and non-metals on the right-hand side

• Between the metals and the non-metals lie the elements which display some properties of both

• These elements are referred to as metalloids or semi-metals

A zig-zag line in this diagram separates the metals on the left, from the non-metals on the right

Properties of metals and non-metals

Identifying Trends

Extended tier only

• Using given information about elements, we can identify trends in properties 

• An example of this could be determining the trend in reactivity of Group I metals 

Reaction of lithium with water:

lithium  + water   →   lithium hydroxide  +  hydrogen 

2Li (s)  +  2H₂O (l)   →   2LiOH (aq)  +   H₂ (g)

• Observations:

  • Relatively slow reaction

  • Fizzing

  • Lithium moves on the surface of the water 

Reactions of sodium with water:

sodium + water   →   sodium hydroxide  +  hydrogen 

2Na (s)  +  2H₂O (l)   →   2NaOH (aq)   +   H₂ (g)

• Observations:

  • More vigorous fizzing 

  • Moves rapidly on the surface of the water

  • Dissolves quickly 

Reactions of potassium with water:

potassium  + water   →   potassium hydroxide  +  hydrogen 

2K (s)  +  2H₂O (l)   →   2KOH (aq)  +   H₂ (g)

• Observations:

  • Reacts more vigorously than sodium 

  • Burns with a lilac flame 

  • Moves very rapidly on the surface 

  • Dissolves very quickly

Identifying the trend

• The trend:

  • The observations show that reactivity of the Group I metals increases as you go down the group

• Using the trend:

  • With this information we can predict the trend going further down Group I for the elements rubidium, caesium and francium

• Predicting properties:

  • Reactivity increases down the group

    • Lithium is the least reactive metal at the top of the group

    • So, francium will be the most reactive at the bottom of the group

  • This means that rubidium, caesium and francium will react more vigorously with air and water than lithium, sodium and potassium

• Predicted reactions with water:

  • Rubidium reacts very violently and may explode

  • Caesium reacts extremely violently and can explode

  • Francium is extremely reactive, but it is rare and radioactive so it is difficult to confirm predictions