3.1.1

The Periodic Table

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The Periodic Table - Groups and Periods

The periodic table is arranged into periods and groups.

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The periodic table

  • The periodic table is the table that organises all the elements into groups and periods.
    • The elements are arranged in order of proton number, starting with hydrogen that has the proton number of 1.
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Periods

  • A period is a row in the periodic table.
    • Elements in the same period have their valence electrons in the same shell.
  • The diagram highlights Period 3.
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Period example

  • Magnesium and sulfur are in the same period.
    • In simple terms, they have the electron configuration 2,8,2 and 2,8,6 respectively.
    • So, their valence electrons are in the same shell.
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Groups

  • A group is a column in the periodic table.
  • Elements in the same group have their electrons in similar orbitals.
    • They often have very similar properties.
    • A Group n element has n valence electrons.
      • E.g. Carbon is in Group 4 and has 4 valence electrons.
  • The diagram highlights Group 7.
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Group example

  • The halogens are all in Group 7.
    • Fluorine's simplified electron configuration is 2,7.
    • Chlorine's is 2,8,7.
      • We see they both have the same number of valence electrons.
  • We also know that halogens have very similar chemical properties.

Periodic Table - Blocks

The periodic table can be organised into four sections. These are labelled s, p, d and f blocks.

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The s block

  • The two leftmost columns make up the s block.
    • This is called the s block because elements in it have all their valence electrons in s orbitals.
    • Note, Helium is also an s block element because it has the electron configuration 1s2.
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The p block

  • The six rightmost columns make up the p block.
    • This is called the p block because elements in the p block have a partially filled p sub-shell.
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The d block

  • The d block lies between the s and p blocks.
    • Elements in the d block have a partially filled d sub-shell.
    • Elements in the d block are often called transition metals.
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The f block

  • The f block is detached along the bottom of the periodic table.
    • Elements in the f block have a partially filled f sub-shell.
    • These elements are referred to as the lanthanides and the actinides (top and bottom row respectively).

Jump to other topics

1Physical Chemistry

2Physical Chemistry 2 (A2 Only)

3Inorganic Chemistry

4Inorganic Chemistry 2 (A2 Only)

5Organic Chemistry 1

6Organic Chemistry 2 (A2 Only)

6.1Optical Isomerism (A2 Only)

6.2Aldehydes & Ketones (A2 Only)

6.3Carboxylic Acids & Esters (A2 Only)

6.4Aromatic Chemistry (A2 Only)

6.5Amines (A2 Only)

6.6Polymers (A2 Only)

6.7Biological Organic (A2 Only)

6.8Organic Synthesis (A2 Only)

6.9NMR Spectroscopy (A2 Only)

6.10Chromatography (A2 Only)

6.11A-A* (AO3/4) - Organic 2

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