EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:1.6 4 Ionic Bonds: Dot & Cross Diagrams

EDEXCEL IGCSE CHEMISTRY: DOUBLE SCIENCE 复习笔记:1.6 4 Ionic Bonds: Dot & Cross Diagrams

Ionic Bonds: Dot & Cross Diagrams

 

Deducing Dot & Cross Diagrams for Ionic Compounds

  • Sodium is a group 1 metal so will lose one outer electron to another atom to gain a full outer shell of electrons
  • A positive sodium ion with the charge 1+ is formed
  • Chlorine is a group 7 non-metal so will need to gain an electron to have a full outer shell of electrons
  • One electron will be transferred from the outer shell of the sodium atom to the outer shell of the chlorine atom
  • A chlorine atom will gain an electron to form a negatively charged chloride ion with a charge of 1-

 

Formula of ionic compound:    NaCl

 

 

Ionic-bonding-%E2%80%93-Sodium-ChlorideSodium chloride ionic bonding

 

Exam Tip

For exam purposes you need only show the outer electrons in dot & cross diagrams.You should be able to draw dot & cross diagrams for combinations of ions from groups 1,2,3,5,6 and 7.

 

Magnesium Oxide Dot & Cross Diagram

  • Magnesium is a group 2 metal so will lose two outer electrons to another atom to have a full outer shell of electrons
  • A positive ion with the charge 2+ is formed
  • Oxygen is a group 6 non-metal so will need to gain two electrons to have a full outer shell of electrons
  • Two electrons will be transferred from the outer shell of the magnesium atom to the outer shell of the oxygen atom
  • Oxygen atom will gain two electrons to form a negative ion with charge 2-

 

Formula of ionic compound:    MgO

 

Magnesium-Oxide-dot-cross-diagram

 

Diagram showing the dot-and-cross diagram of magnesium oxide

 

 

Exam Tip

When writing about ions, we use the notation 1-, 2+ etc. to describe the charge of the ion, with the number first followed by the sign (+/-). It is incorrect to write them the other way around as this refers to the oxidation state, not the charge.

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