Group 2 elements have 2 electrons in their outer shells and lose these to form 2+ ions
1 of 6
Reactivity of Group 2 Elements
As you go down the group ionisation energies decrease, due to:
increasing atomic radius
shielding effect
When Group 2 elements react they lose electrons to form positive ions
The easier to lose electrons, the more reactive the element
Reactivity increases down the group
2 of 6
Group 2 Elements react with Water and Oxygen
When Group 2 elements react, the are oxidised from a state of 0 to +2
Group 2 metals react with water to give a metal hydroxide and hydrogen
M + 2H2O = M(OH)2 + H2
Oxidation numbers
0 +2
Group 2 metals burn in oxygen to form solid white oxides
2M + O2 = 2MO
Oxidation numbers
0 +2
0 -2
3 of 6
Group 2 Oxides and Hydroxides
The oxides of the Group 2 metals react readily with water to form metal hydroxides, which dissolve. The hydroxide ions (OH-) make alkaline solutions
Magnesium oxide is an exception, it only reacts slowly and the hydroxide isn't very soluble
The oxides form more strongly alkaline solutions as you go down the group, because the hydroxides get more soluble
4 of 6
Thermal Stability
Thermal decomposition is when a substance breaks down when heated. The more thermally stable a substance is, the more heat it will take to break it down
Group 2 carbonates decompose to form the oxide and carbon dioxide:
MCO3 = MO + CO2
Thermal stability increases down the group
5 of 6
Neutralising Acids
Group 2 elements are known as the alkaline earth metals, and many of their common compounds are used for neutralising acids
Calcium hydroxides is used in agriculture to neutralise acid soils
Magnesium hydroxide is used in some indigestion tablets as an antacid
Comments
No comments have yet been made