Group 1 and 2 Flashcards
Group 1 reaction with water
Form hydroxide and hydrogen. Lithium reacts steadily with cold water with fizzing, sodium forms shiny bead that moves around on surface. Potassium catches fire.
Group 1 reaction with chlorine
Form MCl, colourless and ionic
Properties of G1 hydroxides
White solids, soluble in water forming alkalis. Strong base
Properties of G1 carbonates
M2CO3. Dissolve in water. Form alkaline solutions. Do not decompose on heating except lithium.
Properties of G1 nitrates
White crystalline solids MNO3.
Decompose to nitrite (MNO2), giving off O2.
Lithium nitrate decomposes to NO2, Li2O, O2
Flame colours of group 1 metal compounds
Lithium - bright red Sodium - orange-yellow Potassium - lilac Rb+ Red Cs+ Blue
Group 1 element properties compared to group 2
G2 harder and denser and higher melting.
G2 reaction with O2
Burn readily apart from Be to form MO. Barium forms BaO2 peroxide.
G2 reaction with water
Not as vigorous as G1, rate decreases down group.
Make hydroxides.
What happens in solubility down group 2 hydroxides?
More soluble down group
Flame colours of group 2 metals
Beryllium - no colour Magnesium - no colour Calcium - brick red Strontium - bright red Barium - pale green
Thermal stability down both group in carbonate (and nitrate)
As you go down group, cations larger and charge same, decreasing charge density. This decreases polarisation on carbonate. This means that the C-O is less weakened than if it was polarised so CO2 and O2- (products of thermal decomp) are formed less easily. Increasing thermal stability.
Thermal stability in nitrates and carbonates from group 1 to 2.
Cation has higher nuclear charge, decreasing ionic radius. Charge doubled, doubling charge density. Group 2 polarises anion more, decreasing thermal stability.
What happens in solubility down group 2 sulfates?
Less soluble down group
G1 nitrate thermal decomp
nitrite an d oxygen
