Predicting Structures (Edexcel AS Chemistry)

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Predicting Structure & Bonding

  • Different types of structure and bonding have different effects on the physical properties of substances such as their melting and boiling points, electrical conductivity and solubility

Characteristics of Different Compound Structure Types Table

Characteristics of different compound structure types table, downloadable AS & A Level Chemistry revision notes

Worked example

Predicting Physical Properties

Bonding & structure

The table below shows the physical properties of substances X, Y and ZWorked Example - Bonding and Structure, downloadable IB Chemistry revision notes

Which one of the following statements about X and Y is completely true?

Statement 1: X has a giant ionic structure, Y has a giant molecular structure, Z is a metal

Statement 2: X is a metal, Y has a simple molecular structure, Z has a giant molecular structure

Statement 3: X is a metal, Y has a simple molecular structure, Z has a giant ionic structure

Statement 4: X has a giant ionic structure, Y has a simple molecular structure, Z is a metal

Answer

The correct answer is Statement 4

    • The relatively high melting point, solubility in water and electrical conductivity when molten suggest that X is a giant ionic structure.
    • The low melting point of Y suggests that little energy is needed to break the lattice which corresponds to a simple molecular structure. This is further supported by the low electrical conductivity and its being almost insoluble in water.
    • Compound Z has a very high melting point which is characteristic of either metallic or giant molecular lattices, however since it conducts electricity, compound Z must be a giant metallic lattice.

Worked example

Bonding & structure

Compound X has the following properties:4.1.14 Worked Example 2, downloadable IB Chemistry revision notes

What is the most probable structure of X?

A. Network covalent

B. Polar covalent molecule

C. Ionic lattice

D. Metallic lattice

Answer:

The correct option is A

    • A high melting point is characteristic of a giant structure, which could be metallic, ionic or covalent
    • The poor conductivity as a liquid and solid would match a giant covalent or network covalent structure

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Philippa

Author: Philippa

Expertise: Chemistry

Philippa has worked as a GCSE and A level chemistry teacher and tutor for over thirteen years. She studied chemistry and sport science at Loughborough University graduating in 2007 having also completed her PGCE in science. Throughout her time as a teacher she was incharge of a boarding house for five years and coached many teams in a variety of sports. When not producing resources with the chemistry team, Philippa enjoys being active outside with her young family and is a very keen gardener.