2. Group 2, alkaline earth metals
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What are the elements in group 2 called?
The alkaline earth metals
What is atomic radius?
The distance from the centre of the nucleus to the outer electrons
What happens to atomic radii down group II?
It increases
Why does atomic radius increase down group II?
• more shells as you move down the group • so increased distance from nucleus • so atomic radius ↑
What is the first ionisation energy?
The enthalpy change when 1 mole of gaseous atoms forms one mole of positive gaseous atoms (by losing 1 mole of electrons)
What happens to first ionisation energy down group II?
Decreases
Why does first ionisation energy decrease down group II?
• more shells down group • outer electrons so ↑ distance from nucleus • so increased shielding • so weaker attraction for outer electrons
What is melting point?
The point at which sufficient bonds are broken/loosened within the substance so that the solid and liquid phase are in equilibrium
What happens to the melting point down group II?
Decreases
Why does melting point decrease down group II?
• Metals held by metallic bonds * Atomic radii ↑ down group but same number of delocalised electrons = less attraction between metal ions and electrons
What is the irregularity in the trend that melting point decreases down group II?
Mg
Why is Mg an irregularity in the trend that melting point decreases down group II?
It has a different crystal structure from the other elements, which is less packed and therefore easier to separate
Which group II compounds react with water?
All of them
What do group II compounds react with water to produce?
The metal hydroxide and hydrogen
What is the rate of reaction when Mg reacts with water?
Very slow
What is the equation for the reaction of Mg with water?
Mg₍ₛ₎ + H₂O₍ₗ₎ → Mg(OH)₂₍ₐᵩ₎ + H₂₍𝓰₎
What happens when Mg is heated in steam?
It will burn to form an oxide
What is the equation for the reaction of Mg with steam?
Mg₍ₛ₎ + H₂O₍𝓰₎ → MgO₍ₛ₎ + H₂₍𝓰₎
For group II elements, from calcium to barium, how do they react with cold water down the group?
React with increasing vigour down the group
Why do group II elements, from calcium to barium, react more vigorously with water down the group?
• more likely to lose electrons • larger atom/more shells • greater distance from nucleus to outer electrons • ↑ shielding • easier to lose outer electrons
What is solubility?
The maximum amount of solute that will dissolve in a given volume of solvent (i.e. how easily it dissolves)
How soluble is something when it is ‘sparingly soluble’?
Not very soluble
Why is Mg(OH)₂ considered to be sparingly soluble?
A very small amount of it dissolves, giving a suspension of magnesium hydroxide in water (milk of magnesia)
How is milk of magnesia formed?
Magnesium hydroxide is dissolved, giving a suspension in water