Group 2 The Alkali Earth Metals

Group 2: Properties of Group II Elements

Group 2: Properties of Group II Elements

The group II elements are known as the alkali earth metals. They are all reactive metals and, apart from magnesium and calcium which are found abundant within the Earth’s crust, are relatively rare.

Group II elements have the outer shell configuration ns2.

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Properties of individual atoms

  • Atomic size: as you descend the group there is a rise in the number of shells. This means that the outer shells are shielded more from the nucleus and so are not held so tightly. Therefore, the size of the atoms increases.
  • First ionisation energies: as you descend the group there is a rise in the number of shells. This means that the outer shells are shielded more from the nucleus and are not held so tightly making them easier to remove. Therefore, there is a decrease in first ionisation energies.
  • Electronegativities: as you descend the group there is a rise in the number of shells. This means that the outer shells are shielded more from the nucleus and are not held so tightly. Therefore, there is a decrease in electronegativities.

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Melting points and electrical conductivity

Cations become harder to separate the stronger the metallic bonding is. Therefore, the stronger the metallic bonding the higher the melting point.

As you descend the group, the cation size increases while the cation charge does not change. Therefore, there is a decrease in charge density so the attraction between cations and delocalized electrons decreases. This means that the melting point and hardness also decrease.

There are, however, discrepancies between magnesium and calcium and between strontium and barium. This is because a change in crystal structure alters the distance between ions and, therefore, the metallic bonding strength.

  • Be and Mg have hcp structures
  • Ca and Sr have fcc structures
  • Ba has a bcc structure
Element Structure Size of cation (nm) Tm (