Edexcel A Level Chemistry:复习笔记1.5.8 Predicting Structures
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
Predicting Physical Properties
Worked Example
Bonding & structure
The table below shows the physical properties of substances X, Y and Z
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:
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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