Group 2, The Alkali Earth Metals

This is not mine, it is from this lovely website here:

They are from the AQA section but are useful to anyone that does group 2 in their A-level

 These notes go into more detail than is necessary, and I am hoping to upload condensed versions soon :)

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  • Created on: 31-05-13 19:01
Preview of Group 2, The Alkali Earth Metals

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Topic 2.6
Trends in size, first ionization energy and electronegativity
Trends in reaction with water
Trends in solubility of group 2 sulphates and hydroxides

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The elements of group II are known as the alkali earth metals.
All of these elements are reactive metals. Magnesium and calcium are abundant in the earth's
crust. The others are relatively rare.
Group II elements have the outer shell configuration ns2.
1. Properties of individual atoms
a) atomic size
On descending a group, the number of shells increases. Therefore the outer shells are more
shielded from the nucleus, are less closely held and move further away.…read more

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In fact, there are discrepancies between magnesium and calcium and between strontium and
barium. This is due to the change in crystal structure, which affects the distance between the ions
and thus the strength of the metallic bonding. Be and Mg have hcp structures, Ca and Sr have
fcc structures and Ba has a bcc structure.
Element Size of Tm/oC
Be (hcp) 0.027 1278
Mg (hcp) 0.072 649
Ca (fcc) 0.100 839
Sr (fcc) 0.113 769
Ba (bcc) 0.…read more

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Reaction of group II elements with water
Metals react with water to form metal hydroxides and hydrogen.
e.g. Ca(s) + 2H2O(l) Ca2+(aq) + 2OH(aq) + H2(g)
The vigour of these reactions depends on two factors:
how easily two electrons can be removed from an atom
how soluble the hydroxides of the metals are
Since ionisation energies decrease down a group, the electrons are more easily removed from
the atoms and the reaction with water becomes increasingly vigorous on descending group II.…read more

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The compounds formed by the elements of group II are predominantly ionic.
The solubility of ionic compounds depends on the balance between the attraction of the
oppositely charged ions to each other and the attraction of the separate ions to water.
If the attraction of the ions to each other is stronger than their attraction to water, the
compounds will not be soluble.…read more

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The solubility of the group II hydroxides increases on descending the group.
Mg(OH)2 is insoluble, Ca(OH)2 is sparingly soluble and Sr(OH)2 and Ba(OH)2 are
If dilute sodium hydroxide is added to a solution of Mg2+ ions, a white precipitate will be
formed immediately:
Mg2+(aq) + 2OH(aq) Mg(OH)2(s)
If dilute sodium hydroxide is added to a solution of Ca2+ ions, a faint white precipitate will be
formed (excess NaOH must be added).…read more


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