2.2.3

Electronic Configuration of Elements

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Electronic Configuration of Elements and the Periodic Table

Electronic configuration shows electron shells (e.g. 2,8,8). Groups are outer electrons, and periods are shells. Noble gases have full outer shells, making them stable.

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What is electronic configuration?

  • Electronic configuration shows how electrons arrange in shells around an atom's nucleus.
    • Each shell holds a certain number of electrons: 2 in the first, 8 in the second, and 8 in the third for elements 1-20.
  • The number of protons (atomic number) equals the number of electrons in a neutral atom.
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Writing electronic configurations for elements 1-20

  • Start filling electrons from the innermost shell outward.
    • Example for Oxygen (8): 2 electrons in shell 1, and 6 electrons in shell 2 (2,6).
    • Example for Calcium (20): Shell 1 has 2, shell 2 has 8, shell 3 has 8, shell 4 has 2 (2,8,8,2).
  • Write numbers separated by commas to show electrons in each shell.
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Electronic configuration of ions

  • Ions form when atoms gain or lose electrons to become charged.
  • Write the electronic configuration of an ion based on its new number of electrons.
    • Example: Na+ ion loses 1 electron, so configuration of Na+ is 2,8.
    • Example: O2- ion gains 2 electrons, so configuration is 2,8.
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Noble gases have full outer shells

  • Group VIII (18) are the Noble Gases.
  • These gases have full outer electron shells, making them very stable.
    • Examples: Helium (2 electrons) and Neon (2,8) have full outer shells.
  • This stability explains why Noble Gases do not easily form ions or react.

Jump to other topics

1States of Matter

2Atoms, Elements & Compounds

3Stoichometry

4Electrochemistry

5Chemical Energetics

6Chemical Reactions

7Acids, Bases & Salts

8The Periodic Table

9Metals

10Chemistry of the Environment

11Organic Chemistry

11.1Formulae, Functional Groups & Terminology

11.2Naming Organic Compounds

11.3Fuels

11.4Alkanes

11.5Alkenes

11.6Alcohols

11.7Carboxylic Acids

11.8Polymers

12Experimental Techniques & Chemical Analysis

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