Group 2, the alkaline earth metals
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Why are group 2 elements called the alkali earth metals?
Because their oxides and hydroxides are alkaline.
Which block of the periodic table are group 2 elements in?
S - block
How does the reactivity of group 2 compare to group 1?
They react similarly but are less reactive.
What is the outer electron configuration of group 2 elements?
They have two electrons in their highest energy s sub-shell.
What ion do group 2 elements form?
M2+ ions as they lose two electrons.
Why does atomic radius increase down group 2?
Each element has an additional filled electron shell compared to the one above.
Why do group 2 elements generally have high melting points?
They form metallic bonds and giant metallic structures.
Why does melting point decrease down group 2?
• Ions get bigger • Weaker attraction between metal ions and delocalised electrons • Weaker metallic bonds
Which group 2 element is anomalous for melting point?
Magnesium as it has the lowest boiling point.
What happens to 1st and 2nd ionisation energies down group 2?
Both decrease.
Why does ionisation energy decrease down group 2?
• Outer electron is in a higher energy level • More shielding • Atoms are larger (more shells) • Weaker attraction between nucleus and outer electron
What happens to group 2 elements in reactions in terms of oxidation?
They are always oxidised (lose 2 electrons)
What is the general equation for group 2 metals reacting with liquid water?
M (s) + 2H2O (l) –> M(OH)2 (aq) + H2(g)
How does reactivity with water change down group 2?
Reactivity increases (reactions become more violent)
What is the pH of group 2 hydroxide solutions?
Greater than 7 (alkaline)
How does Magnesium react with cold water?
Very slowly; bubbles of H2 take several hours to appear.
What is another name for Magnesium hydroxide and what is it used for?
Milk of magnesia, used as an indigestion remedy to neutralise stomach acid.
How does Calcium react with cold water?
Vigorous reaction; fast bubbling and mixture heats up.
How does Magnesium react with steam?
More vigorously than with cold water; forms MgO and H2. Mg (s) + H2O (g) –> MgO (s) + H2 (g)
How does steam reactivity change down group 2?
Reactions become increasingly vigorous down the group.
What is the general formula of group 2 hydroxides?
M(OH)2
What is the general formula of Group 2 sulfates?
MSO4
What is the trend in solubility of group 2 hydroxides down the group?
Increases down the group.
What is the trend in solubility of group 2 sulfates down the group?
Decreases down the group.