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IB DP Chemistry: SL復習筆記4.1.2 Ionic Compounds

Category: IB課程, 教材筆記, 福利干貨 Date: 2022年8月4日上午11:17

Ionic Lattices

The ions form a?lattice?structure?which is an evenly distributed?crystalline?structure
Ions in a lattice are arranged in a?regular?repeating?pattern?so that positive charges cancel out negative charges
Therefore the final lattice is overall electrically?neutral

1.3-Chemical-Bonding-Ionic-Lattice

Ionic solids are arranged in lattice structures

Properties of Ionic Compounds

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

Ionic bonding & giant ionic lattice structures

Ionic compounds are?strong
- The?strong electrostatic forces?in ionic compounds keep the ions strongly together
They are?brittle?as ionic crystals can split apart
Ionic compounds have?high melting?and?boiling?points
- The strong electrostatic forces between the ions in the lattice act in all directions and keep them strongly together
- Melting and boiling points increase with charge density of the ions due to the greater?electrostatic attraction?of charges
- Mg²⁺O^2-?has a higher melting point than Na⁺Cl^-
Ionic compounds are?soluble?in water as they can form?ion - dipole bonds
Ionic compounds only?conduct?electricity?when?molten?or in?solution
- When molten or in solution, the ions can freely move around and conduct electricity
- In the solid state they’re in a fixed position and unable to move around

Characteristics of Giant Ionic Lattices compared to other Structures

1.4-States-of-Matter-Table_4

Worked Example

The table below shows the physical properties of substances X, Y and Z 4.1.2-Worked-Example-Bonding-and-Structure

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 an?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 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