Group 2- Alkaline Earth Flashcards
What is the outer electron configuration?
ns2
What type of elements are they?
Metallic solids
Compare the boiling, melting point and enthalpy of atomisation with group 1
They are all higher than group 1
This is because they have stronger metallic bonding in their lattice
- they have 2 delocalised electrons rather than 1 per atom in lattice
What is the chemistry based on?
The +2 oxidation state
What stabilises ionic group 2 compounds?
Low 1st and 2nd I.E. And high lattice enthalpy of salts
It is favourable for them to be ionic compounds
Why are group 2 metals less reactive than group 1 metals?
They have a coating of oxide on their surface
Which element is an exception?
Beryllium
Describe the trend in IE down the group
It decreases due to more shells and lower zeff (increased shielding)
This means electrons are easier to remove
Describe the trend in atomic radius down the group
The radius increases due to more shells
Which structure is BeCl2 similar to?
It is similar to Alcl2 apart from Be has dative colavent bonds to Cl due to high degree of covalent character
Why is beryllium an exception?
Be2+ is small and so highly charge dense
This means it is strongly polarising and has a high degree of covalent character
It draws electrons towards itself
Why is Be2+ acidic in solution?
Due to its polarising power
Give examples where Be is an exception
It doesn’t react with water
Be compounds have greater covalent character
Beryllium is amphoteric
Be2+ is acidic whereas others are neutral
Describe the trend of covalent character down the group
As the group descends, the atoms become more electronegative and so they decrease in covalent character
What is the most common group 2 organometallic
Those that contain Mg
Mg has high charge density so they have a high degree of covalent character
Carbon is negatively polarised- nucleophiles
How is a Grignard reagent formed?
RX + Mg -> RMgX
Describe the reactivity of group 2 organometallics
They are very reactive
What properties are unexpected of heavier G2 atoms?
They are more ionic that expected
They are kinetically unstable
They are thermodynamically unstable
Show equations for dissolve KCl, lattice enthalpy and hydration
Solvation
kCl -> k+(aq) + Cl-(aq)
Lattice enthalpy
kcl -> k+(g) + Cl-(g)
Hydration
k+(g) + Cl-(g) -> k+(aq) + Cl-(aq)
How can you calculate the enthalpy of solvation (when a solid dissolves and forms aqueous ions)
Solvation= lattice enthalpy - hydration of ions
Hydration of Ions= lattice enthalpy + solvation
Describe the entropy changes when a crystal dissolves
1) breaking down ordered lattice (increase)
2) solvation of ions (decrease)- hydrogen bonds
Describe how temperature plays a part in solubility
As temperature increases T^S increases
^G becomes more negative (more spontaneous)
The salt becomes more soluble
What is the trend between coordination as you go down the group?
Coordination to Ligands is weaker down the group as charge density decreases
