8.3.1

The Halogens - Properties

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Halogens (Group 7) - Properties

Elements in group 7 in the periodic table are called halogens. They have 7 electrons in their outer shell. They are very reactive because they easily accept an electron into this outer shell. They have similar properties and react in similar ways.

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7 outer electrons

  • Halogens are in group 7 and so have 7 electrons in their outer shell.
  • When they react, they gain 1 electron to get a full outer shell.
  • By gaining 1 electron, they form a negative ion.
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Diatomic molecules

  • In their elemental form, halogens share electrons to make diatomic molecules (molecules made of pairs of atoms).
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Salts

  • When a metal atom transfers its outer electron to a non-metal atom (like a group 7 atom), salts are formed.
  • The result is a compound where all the ions have a full outer shell.
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Reactivity

  • As you go down the group, the halogens become less reactive. This is because:
    • The atoms gain more electron shells.
      • The outer electron shell is further from the nucleus.
        • The attraction between the nucleus and the electron (to be gained from another element) decreases.

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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