Master this deck with 45 terms through effective study methods.
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The ionisation energies of group 2 elements decreases down the group. This is because - The atomic radius is larger as there is +1 quantum shell each time - Therefore increased shielding to the outer electron - These factors outweigh the increase in proton number
General increase in reactivity - Due to differences in metallic radii - Sum of first and second ionisation energies decreases
2M(s) + O2(g) ——> 2MO(g)
- extremely bright flame - formation of a white solid powder
They react slowly with oxygen without the presence of a flame to form a dull oxide layer, preventing further reaction.
To prevent reaction with oxygen or water vapour in the air.
M(s) + Cl2(g) ——> MgCl2(s)
M(s) + 2H2O(l) ——> M(OH)2(aq) + H2(g)
Calcium hydroxide (sparingly soluble in water) therefore the vessel will go cloudy.
Effervescence
They react with water to form alkalis
MO(s) + H2O(l) ——> M(OH)2(aq/s) O2- + H2O —> 2OH-
Increases down the group
Bubble gas through limewater (hydrated calcium hydroxide). Limewater will go cloudy if CO2 present. CO2(g) + Ca(OH)2(aq) ——> CaCO3(s) + H2O(l)
MO + acid ——> metal salt + water
M(OH)2 + acid ——> metal salt + water
Soluble: Magnesium sulfate Sparingly soluble: Calcium sulfate Insoluble: Strontiium and barium sulfate.
- add acidified barium chloride / nitrate solution, white barium sulfate ppt will form Ba 2+ (aq) + SO4 2- (aq) ——> BaSO4(s)
To prevent the formation of barium carbonate and forming a false positive white ppt.
Indication of how stable a compound is when it is heated. Something which does not undergo thermal decomposition would be classed as thermally stable.
Complex carbonate /nitrate ions decompose into more stable compounds, rather than being free ions in the molten phase.
As you go down group 2, thermal stability increases. This is because: - The metal cations become less charge dense as their ionic radii increase - Therefore the polarising power of the cation decreases - Therefore the N-O bonds / C-O bonds are weakened/polarised/distorted less.
Metal nitrate ——> metal oxide + NO2 + O2
Brown fumes (nitrogen dioxide)
Metal nitrate ——> metal nitrite + O2
Lithium nitrate will decompose the same way as group 2 nitrates as Li+ is an incredibly charge dense ion therefore reacts similarly to charge dense 2+ group 2 ions.
metal carbonate ——> metal oxide + CO2
There is no visible change as CO2 is colourless and both the carbonates and oxides are white solids.
Yes - but at VERY high temperatures.
To distinguish metal ions in compounds.
- wear safety goggles - add a few drops of conc. HCl to the metal sample so some dissolves, allowing the formation of metal chlorides. - Dip a clean nichrome wire loop into concentrated HCl, then into the sample - Place the wire INTO a roaring (blue) Bunsen flame and observe the colour.
Chlorides are the most volatile salts therefore produce the best results.
- many compounds contain sodium impurities, so sodium colours often mask other colours. - colour observation is subjective
Red
Yellow-orange
Lilac
Red-purple
Blue - violet
No colour
No colour
Brick red
Crimson red
Apple green
- electrons absorb heat energy and are 'excited' to a higher energy level - electrons return to ground state releasing energy which corresponds to a specific wavelength(s) of light. - if the wavelength of light is within the visible spectrum, a colour will be observed.
- Add warm NaOH releasing ammonia gas: NH4+ + OH- —-> NH3(g) + H2O Either: - hold damp litmus paper above, turns litmus paper red to blue as it is alkali OR - HCl gas reacts with ammonia gas to form white, misty NH4Cl fumes: NH3(g) + HCl(g) —-> NH4Cl