2.2 - Group 2 Metals Flashcards
(31 cards)
What happens to atomic radius down group 2
Atomic radius increases down the group.
As one goes down the group, the atoms have more shells of electrons making the atom bigger.
what happens to melting point down group 2?
Melting points decrease down the group.
The metallic bonding weakens as the atomic size increases.
The distance between the positive ions and delocalized electrons increases.
Therefore the electrostatic
attractive forces between the positive ions and the delocalized electrons weaken
what happens to first ionisation energy down group 2?
The outermost electrons are held more weakly because they are successively further from the nucleus in additional shells.
In addition, the outer shell electrons become more shielded from the attraction of the nucleus by the
repulsive force of inner shell electrons
so Ionisation energy decreases down the group
What happens to reactivity down group 2
Increases
Magnesium and steam reaction
Produces magnesium oxide and hydrogen
bright white flame
Mg + H2O —> MgO +H2
magnesium reacts with warm water reaction
produces magnesium hydroxide and hydrogen
No flame
Mg + 2H2O —> Mg(OH)2 +H2
Other group two metals and COLD water reaction
produce hydroxide and hydrogen gas
observations for other group 2 metals reacting with cold waterq
Down the group -
fizzing
metal dissolving
solution heating up
calcium - white precipitate appears
why is magnesium used to extract titanium?
abundant
low density
corrosion resistant
steps in extracting titanium
- TiO2 is converted to TiCl4 @ 900’
- TiCl4 is purified by fractional distillation in an argon atmosphere
- Ti is extracted by Mg in an argon atmosphere @ 500’
equations for using magnesium to extract titanium
TiO2 + 2Cl2 +2C —-> TiCl4 + 2CO
TiCl4 + 2Mg —–> Ti + 2MgCl2
Extraction of titanium is expensive because
- The expensive cost of the Mg
- This is a batch process which makes it expensive because the
process is slower (having to fill up and empty reactors takes time) and requires more labour and the energy is lost when the reactor is cooled down after stopping - The process is also expensive due to the argon, and the need to
remove moisture (because TiCl4
is susceptible to hydrolysis). - High temperatures required in both steps
what happens to solubility to group 2 hydroxides down the group?
increases
what do all group 2 hydroxide appears as when not soluble?
white precipitates
is magnesium hydroxide soluble in water?
no
Ionic equation for formation of Mg(OH)2
Mg2+(aq) + 2OH-(aq) –> Mg(OH)2 (s).
what is magnesium hydroxide used for in medicine?
used as milk of magnesia to neutralise excess acid in the stomach that would cause indigestion
magnesium hydroxide reacting with excess hydrochloric acid
Mg(OH)2 + 2HCl —> MgCl2 + 2H2O
what is calcium hydroxide used for?
neutralises acidic soil
test for carbon dioxide - lime water test
Ca(OH)2 (aq) + CO2 (g) –> CaCO3 (s) + H2O(l)
what happens to group 2 sulphates down the group?
they become less solube
which is the least soluble group 2 sulphate
BaSO4
what is barium sulphate used for in med?
used as a barium meal
for patients who need x-rays of their intestines
why do we use barium sulphate even though barium is toxic
small amounts of barium is used
its low solubility means it is not absorbed into the blood
