Alkaline earth metals (group 2) 9 Flashcards
size
increase down a group
melting point
high (decrease apart from Mg)
sea of delocalised electrons are further way from the positive nucleus
reaction with water
more reactive going down the group
redox reaction
Mg(s) +2H20(l) —— Mg(OH)2 (aq) + H2 (g)
(magnesium hydroxide is milk of magnesia and is used to neutralise excess stomach acid)
Mg(s) +H20(g) —— MgO + H2(g)
(reacts rapidly wth stream)
hydroxide
magnesium hydroxide = (insoluble)
calcium hydroxide = (sparingly soluble) = limewater
strontium hydroxide= (more soluble)
barium hydroxide = dissloves = strong alkaline solution
sulfate
less soluble going down the group
barium sulphate = outline the gut in x-ray (insoluble)
test for sulphate ions
acidified with nitric/hydrochloric acid
if a sulphate is present a white precipatiate is formed
adding acid removes carbonate ion as carbon dioxide
atomic radius
decrease across a period
Na / Mg / Al
metals
metallically bonded
more delocalised electrons (stronger bonds)
(increased positive charge=more delocalised electrons = decreasing radius)
Si
macromolecular
strong covalent bonds
lots of energy needed to break the the bonds = high melting point
p / S /Cl
melting point depends on the van Der walls
more molecules= more van der walls
weak and easy to overcome
Ar
noble gas
general trend in first ionisation energy
general trend = increase
increasing attraction between the outer shell electrons na the nucleus, due to the number of protons
alkaline earth metals
atomic radius= increase = more shells
first ionisation energy = decrease
reactivity = lose on electron = positive ion
melting point = generally decrease
atomic radii of the group 2 elements
increase
another full shell added each time
shells repel each other
melting point of group 2
decrease
attract of the positive decrease because the distance increase
delocalised electron further from nucleus
strength of metallic bonds decrease
ionisation energy of group 2 Be 900 Mg 738 Ca 590 Sr 550 Ba 503
decrease
easier to lose an electron
distance increase so the delocalised electrons further away, so is easier to remove
magnesium
uses and reasons
extraction of titanium
reduces
added to iron to remove sulphur
more reactive so would displace the iron
magnesium hydroxide Mg(OH)2
uses and reasons
treating acid indigestion increase water (reduces acid)
claim hydroxide Ca(OH)2
uses and reasons
neutralise the soil
strong base
calcium hydroxide solution Ca(OH)2 (aq)
uses and reasons
limewater
test fro carbon dioxide
Barium sulfate BaSO4
main source of commercial barium
test for sulfate ions
coats the inside of intestines so they show up better on the x-ray
uses go magnesium in the extraction of titanium from TiCl4
TiCl4 (l) + 2Mg(s) —- 2MgCl2 (s) + Ti (s)
used in the aerospace industry and in replacement of hips
explain how BaSO4 is insoluble
white precipitate
insoluble
lime kilns
CaCO3 (s)—- CaO(s) + CO2(g)
uses 25 tones of limestone
unlike to be 100% pure
lime (CaO) and slaked lime (Ca(OH)2) used to neutralised soil
CaO(s) + 2HCl (aq) —– CaCl2 (aq) + H20 (l)
Ca(OH)2 (s) + 2HCl (aq) —– CaCl2 (aq) + 2H2O (l)
test for sulfate ions
use acidified BaCl2