Melting Point Trend (AQA A Level Chemistry): Revision Note

Exam code: 7405

Stewart Hird

Last updated

Melting Point Trend

  • The melting points of the oxides vary significantly across Period 3 and show a clear trend

  • Melting point is a clear indication of the forces of attraction which exist between ions, atoms or molecules

 

A graph to show the melting points of the Period 3 Oxides

 

Ionic Oxides

  • The graph starts off showing the melting points of the ionic oxides

    • Sodium oxide

    • Magnesium oxide

    • Aluminium oxide

  • These are ionic oxides because the bonding exists between metals and non metals

  • They have giant lattice structures and thus, high melting points

Giant Covalent Oxides

  • The graph then shows a giant covalent oxide

    • Silicon dioxide

  • This is covalent because both silicon and oxygen are non metals

  • The millions of covalent bonds within this giant structure are extremely strong, and thus it has a high melting point

  • Giant covalent structures can also be called macromolecules or giant molecules

Simple Covalent Oxides

  • The graph then shows a significant drop in melting point, as we reach the simple covalent oxide molecules

    • Phosphorus(V) oxide

    • Sulfur dioxide

    • Sulfur trioxide

  • These are small molecules with only weak intermolecular forces of attraction between them

  • Sulfur dioxide and sulfur trioxide are both gases at room temperature, because both their melting point and boiling point are so low

    • Sulfur trioxide, SO3, has a slightly higher melting point than sulfur dioxide, SO2, because of the increase in intermolecular forces between the slightly larger SO3 molecules

Summary Table of the Physical Properties of the Period 3 Oxides

 

Examiner Tips and Tricks

Make sure that you can state and explain the link between the physical properties of the Period 3 Oxides and their structure and bonding!

You've read 1 of your 5 free revision notes this week

Unlock more, it's free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Stewart Hird

Author: Stewart Hird

Expertise: Chemistry Content Creator

Stewart has been an enthusiastic GCSE, IGCSE, A Level and IB teacher for more than 30 years in the UK as well as overseas, and has also been an examiner for IB and A Level. As a long-standing Head of Science, Stewart brings a wealth of experience to creating Topic Questions and revision materials for Save My Exams. Stewart specialises in Chemistry, but has also taught Physics and Environmental Systems and Societies.

Download notes on Melting Point Trend