AQA A Level Chemistry

Revision Notes

1.4.5 Dot & Cross Diagrams

Representing Dot & Cross Diagrams

  • Dot and cross diagrams are diagrams that show the arrangement of the outer-shell electrons in an ionic or covalent compound or element
    • The electrons are shown as dots and crosses
  • In a dot and cross diagram:
    • Only the outer electrons are shown
    • The charge of the ion is spread evenly which is shown by using brackets
    • The charge on each ion is written at the top right-hand corner

Ionic compounds

  • Ionic bonds are formed when metal atoms transfer electrons to a non-metal to form a positively charged and negatively charged ion
  • The atoms achieve a noble gas configuration

 

Chemical Bonding Ionic Dot & Cross, downloadable AS & A Level Chemistry revision notes

Dot-and-cross diagrams of ionic compounds in which one of the atoms transfers their valence electrons to the other

Covalent compounds

  • The atoms in covalent compounds will share their outer valence electrons to achieve a noble gas configuration

 

Chemical Bonding Covalent Dot & Cross 1, downloadable AS & A Level Chemistry revision notes

Chemical Bonding Covalent Dot & Cross 2 (1), downloadable AS & A Level Chemistry revision notes

Chemical Bonding Covalent Dot & Cross 2 (2), downloadable AS & A Level Chemistry revision notes

Chemical Bonding Covalent Dot & Cross 3 (1), downloadable AS & A Level Chemistry revision notes

 

Dot-and-cross diagrams of covalent compounds in which the atoms share their valence electrons

Worked Example

Draw a dot and cross diagram for lithium nitride

Answer

    • Lithium is a Group 1 metal, so it loses its 1 electron from its outer shell
    • This forms a Li+ ion
    • Nitrogen is a Group 5 non-metal, so it needs to gain 3 electrons to complete its outer shell
    • This forms an N3- ion
    • Overall, three lithium atoms each donate an electron to one nitrogen atom, to form 3 x Li+ ions and 1 x N3-
    • The overall ionic compound formed is Li3N

Chemical Bonding Lithium Nitride Cross Diagram, downloadable AS & A Level Chemistry revision notes

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