4A:Elements of Group 1 and 2 Flashcards
Give some properties of group 1 metals
Less dense than water
Low melting points
Soft
How does ionisation energy change going down group 2 and why?
Decreases
Every element has an extra electron shell
More shielding occurs, distance from the nucleus increases, and effective nuclear charge doesn’t change
How does melting temperature change going down group 2 and why?
Decreases
Charge density decreases as you do down the group so less energy needed to overcome electrostatic attraction
How does atomic and ionic radii change going down group 1 & 2 and why?
Increases
Number of orbitals increases going down the group
What is the first ionisation energy of group 2 metals in comparison to group 1 metals?
Group 2 metals have larger first ionisation energy
As they have an increased nuclear charge but decreased radii
What is the melting points of group 2 metals in comparison to group 1 metals?
Higher melting points
As they lose 2 electrons per atom for metallic bonding therefore it is stronger
What is the electrical conductivity of group 2 metals in comparison to group 1 metals?
Better electrical conductivity
What is the hardness of group 2 metals in comparison to group 1 metals?
Harder than group 1 metals
What is the oxidation number of group 1 and 2 ions?
+1 : Group 1
+2 : Group 2
What are group 1 and 2 metals usually in redox reactions?
Reducing agents
What happens when group 2 metals react with water?
Metal hydroxides (aq) and hydrogen are formed M + 2H2O -> M(OH)2 + H2
How does the reactivity of the group 1 and 2 metals change as you go down?
They get more reactive (outer electron more easily lost)
What happens when group 2 metals react with oxygen?
Burn brightly in air (except beryllium) to form white solids
2M + O2 -> 2MO
What happens when group 2 metals react with chlorine?
Solid white chlorides form (except beryllium which forms a covalent anhydrous chloride)
M + Cl2 -> MCl2
How reactive are group 2 metals in relation to group 1?
Less reactive as group 1 only need to lose 1 electron
Why must Mg and Ca be reacted with steam in order to form their metal oxides?
They are not as reactive as the other group 2 metals
In cold water they form their metal hydroxides instead
What are the oxides and hydroxides of group 2?
Bases (will react with water to form OH- ions
What is the exception to the group 2 oxide bases?
Beryllium oxide - doesn’t react with water & hydroxide is insoluble
Magnesium oxide - reacts slowly & hydroxide isn’t very soluble
How does the strength of the base change going down group 2?
Increases as they become more soluble
As group 2 metal oxides/hydroxides are bases what can they do?
Neutralise dilute acids to form corresponding salts
What is produced when calcium oxide reacts with water?
Reacts quickly to form Ca(OH)2
Limewater
What does amphoteric mean?
A chemical which can react as both an acid or an alkali
How does the solubility of group 2 hydroxides change going down the group?
Becomes more soluble
How does the solubility of group 2 sulphates change going down the group?
Decreases in solubility
What is a barium meal?
Used in medicine as very insoluble (barium sulphate) to highlight areas of the body
What happens when group 2 oxides react with hydrochloric acid?
MO + 2HCl -> MCl2 (aq) + H2O
What happens when group 2 hydroxides react with hydrochloric acid?
M(OH)2 (aq/s) + 2HCl -> MCl2 (aq) + 2H20
What happens when group 2 hydroxides react with sulphuric acid?
M(OH)2 (aq/s) + H2SO4 -> MSO4 (aq/s) + 2H20
What is thermal decomposition?
When a substance breaks down when heated
What does a thermally stable compound do?
Requires more heat to break it down
How can anions be made unstable?
By the presence of a cation
This distorts the anion
What is the affect of the distortion of anions?
Greater the distortion the less stable the compound
How does the size of the cation affect the distortion?
The larger the cation, the less the distortion
As lower charge density
Why do elements in group 1 & 2 become more thermally stable going down the group?
Charge density decreases going down group
Causes less distortion of the anion
Therefore more stable
What is the thermal stability of group 1 in comparison to group 2 metals?
Group 1 compounds are more thermally stable
As greater charge of group 2 metals cause more distortion
What is the thermal stability of group 1 carbonates?
Thermally stable (except lithium carbonate)
What is the thermal stability of group 2 carbonates?
Decomposes easily
MCO3 (s) -> MO (s) + CO2
What is the thermal stability of group 1 nitrates?
Decomposes easily
(Except lithium)
2MNO3 (s) -> 2MNO2 (s) + O2
What is the thermal stability of group 2 nitrates?
Decompose easily
2M(NO3)2 (s) -> MO (s) + 4NO2 + O2
How can you test the thermal stability of nitrates?
How long it takes to produce a certain amount of oxygen
How long until a certain amount of NO2 is produced
How can you test the thermal stability of carbonates?
How long it takes for a certain amount of carbon dioxide to be produced
How does the thermal decomposition change going down group 1 and 2?
Thermal stability increases going down the group
How does the ion size change the polarizing affect?
Smaller cations have a greater polarizing affect
Causing it to decompose more readily
What are the flame colours of group 1 metals?
Li - Red Na - Orange/yellow K - lilac Rb - red Cs - blue
What are the flame colours of group 2 metals?
Ca - brick-red
Sr - crimson
Ba - green
How would you perform a flame test?
Mix compound with a few drops of hydrochloric acid
Heat a piece of platinum in a bunsen flame to clean it
Dip wire into mixture and hold it in the flame
