EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:1.7.2 Covalent Bonds: Dot & Cross Diagrams

EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:1.7.2 Covalent Bonds: Dot & Cross Diagrams

Covalent Bonds: Dot & Cross Diagrams

 

  • Covalent substances tend to have small molecular structures, such as Cl2, H2O or CO2
  • These small molecules are known as simple molecules
  • Small covalent molecules can be represented by dot and cross diagrams
  • You need to be able to describe and draw the structures of the following molecules using dot-and-cross diagrams: hydrogen (H2), chlorine (Cl2), oxygen (O2), nitrogen (N2), hydrogen chloride (HCl), water (H2O), ammonia (NH3) and methane (CH4)
  • The correct dot and cross diagrams for these molecules are shown below:

 

 

Diatomic Molecules

 

Dot & cross representation of a molecule of hydrogen

 

 

Dot & cross representation of a molecule of chlorine

 

 

 

Dot & cross representation of a molecule of oxygen

 

 

 

Dot & cross representation of a molecule of nitrogen

 

 

 

Dot & cross representation of a molecule of hydrogen chloride

 

 

 

Inorganic Molecules

 

Dot & cross representation of a molecule of water

 

 

Dot & cross representation of a molecule of ammonia

 

 

Dot & cross representation of a molecule of carbon dioxide

 

 

 

Organic Molecules

 

Dot & cross representation of a molecule of methane

 

 

Dot & cross representation of a molecule of ethane

 

 

Dot & cross representation of a molecule of ethene

 

 

Exam Tip

Simple covalent molecules are small and can be separated into individual molecular units without breaking any chemical bonds (although there will still be strong covalent bonds holding the atoms in each individual molecule together) Giant ionic and covalent structures form huge continuous networks of atoms that are bonded together and cannot be separated into individual units without breaking bonds.

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