group 2 Flashcards
what is the trend in atomic radius
explain
increases
more electrons so no. energy levels increases, new completed energy level each increment, atoms get bigger.
[ rate of increase decreased due to stronger nuclear charge ]
trend in 1st ionisation energy
decreases
increased atomic distance due to increased no energy levels so further distance between outer electron being removed and nucleus. FoA is weakened
more shielding due to more completed energy levels which decreased FoA between .. .
less energy is needed to overcome FoA
trend in melting points
overall decreases because larger ionic radius of metal ions in giant metallic lattice leads to further distance between +ve nucleus and delocalised system.
more shielding between delocalised system and nucleus
same charge / delocalised e- per atom
so less FoA to overcome
Mg is less than everyone
trend in electronegativity
atomic radius and shielding increases
so bonding is less strong
bonding e- are less strongly attracted to the nucleus
reaction of Mg with cold water
(slow)
Mg + H2O – Mg(OH)2 + H2
reaction on Mg with steam
Mg + H2O – MgO + H2
MgO burns with a white flame
Calcium and water
Ca + 2H2O – calcium hydroxide+ hydrogen
reaction mixture is cloudy bc hydroxide not v soluble
Ca has a protective layer of CaO so there’s a lag
effervescence
alkaline
Ca sinks bc more dense than water
general equation for G2 metals and water
G2 metals and water – metal hydroxide and hydrogen
trend in reactivity
explain
increase; Mg needs a lot of energy whereas Ba happens quickly
outer e- are further from nucleus bc increasing atomic radius;
atoms are bigger;
more e- levels so increased shielding;
e- are lost more easily because eFoA between .. is weaker
equations of Mg in the extraction of titanium
titanium ore = TiO2
TiO2 + C + Cl2 – TiCl4 + CO2
TiCl4 + 2Mg – Ti + 2MgCl2
Mg is used to displace Ti from the chloride compound
trend in solubikity of G2 hydroxides, M(OH)2
increases as go down the group
magnesium hydroxide solubility
use
insoluble almost
used as milk of magnesia, an antacid which neutralised excess stomach acid to help with indigestion
milk of magnesia is a suspension not a solution
calcium hydroxide solubility and use
sparingly soluble; j ab dissolves
slaked lime
- used to neutralise acidic soil
- used by farmers
lime water
- detected carbon dioxide gas by bubbling gas through it, if goes cloudy
- Ca(OH)2 + CO2 – CaCO3 + H20
- calcium carbonate is insoluble therefore white precipitate
Strontium hydroxide solubility
soluble
barium hydroxide solubility and use
readily soluble in aq solution, produces strong alkali;
to soluble is to dissociate
used to test for sulfate ions