Group 2 Flashcards
What is atomic radius? and what is the trend?
Measure of size of an atom
and size of an atom increases down a group
e.g calcium is bigger than magnesium
thats bcs the outer electrons are in a new shell which is further away from the nucleus
What is first ionisation energy?
First ionisation energy decreases down a group
thats bcs e.g Mg and Ca
Mg has 2 full shell and 3rd shell which has 2 more electrons
whereas Ca has 3 full shells with so the 4th shell is further away from the nucleus & more shielding occurs
so the 4th shell electrons experience weaker attraction to nucleus
so it’s easier to remove electron at ca
so calcium has lower first ionisation energy
first ionisation energy decreases down a group
Group 2 elements are all…
alkali earth metals so they bond metallically
All alkaline earth metals are …
solid at room temperatures
Bigger a metals cation…
the lower the melting point
Down group 2 , the cations in metallic lattice
get larger so there is a greater distance between the delocalised electron and the nuclei so there’s a weaker attraction between the delocalised electrons and cation
melting point decreases down group 2
so as we go down group 2 metallic bonding gets weaker
the weaker melting point decreases
What element doesn’t follow the trend of as we go down a group melting point decreases
Magnesium as it’s melting point it’s way lower than all group 2 elements
What is Magnesium used for?
to extract titanium
Separating a metal from its ore is called
extraction
How’s a metal usually used to extract?
They use carbon to react it to extract titanium
e.g by heating iron dioxide with carbon producing iron and carbon dioxide
What happens if we extract titanium with carbon?
if we use titanium oxide with carbon we get titanium carbide and oxygen
which is brittle and makes the metal useless material
so we need another way
How is titanium extracted using magnesium’s
it’s a 2 stage process
where titanium oxide is first heated with carbon and chlorine producing titanium chloride and then magnesium is used to form Titanium and magnesium chloride
in this reaction magnesium donates electrons to titanium so it’s acting as a reducing agent
bcs it’s extracted in 2 stages it’s less efficient then others which is extracted in a continues process
but titanium strength low density and high melting point makes it worth to
Burning fossil fuels like coal produces
sulfure dioxide which is let into the atmosphere which reacts with oxygen to form sulfur trioxide
which has the equation
2SO2 (g) + O2 (g) —> 2SO3 (g)
sulfur trioxide reacts water in clouds to form sulfuric acid
SO3 (g) + H2O (l) —> H2SO4 (aq)
which causes acid rain
How do we stop sulfur dioxide from entering the atmosphere
Calcium provides a way
we get Calcium oxide also known as (quicklime) and mix it with water and produces a mixture called slurry
this slurry is sprayed over the sulfur dioxide gas in a special designed gas which forms calcium sulfide and water
bcs this CaSO3 is a solid it can be dried and collected safely
quicklime is readily available
process is used also to react
calcium carbonate ?known as lime stone
and mix it with water to form a slurry and spray it over the sulfur dioxide and collect the calcium sulfide
this method is known as wet scrubbing
it reduces acid rain by 98%
what do we use to prevent acid rain
burning fossil fuels gives off sulfur dioxide which causes acid rain
we can prevent this by spraying slurry of calcium oxide or calcium decarbonise over the sulfuric dioxide gas and collect the calcium sulfide that forms
Calcium and water react to form
calcium hydroxide and hydrogen
Down group 2 when water water reacts with them
they form hydroxides
the speed of this reaction increases down the group
beryllium does not react at all with water at room temperature
Magnesium reacts very slightly with water at room temperature. but reacts rapidly with steam. Give the balanced chemical equation for these 2 reactions
room temp water
Mg (s) + 2H2O (l) —> Mg(OH)2 (aq) + H2
steam
Mg (s) + H2O (g) —> MgO (s) + H2 (g)
Solubility of group 2 hydroxides
increases down a group
magnesium oxides is hardly soluble
so if magnesium hydroxide forms in a reaction with water it will precipitate out as a white solid
How do first ionisation energy and 2nd ionisation energy vary down group 2
first ionisation energy decreases down the group this causes the atomic/ionic radius to increase
therefore, the attraction between the nucleus and the 2 outermost electrons will decrease down the group
number of electron shells increase down the group this causes the atomic/ionic radius to increase therefore the attraction between the nucleus and the 2 outermost electrons will decrease down the group
the reactivity of group 2 metals with water
increases down the group bcs the sum of the first ionisation and second ionisation energies decreases down the group. therefore the activation energy required to form a metal hydroxide decreases
Write the full balanced equation of the reaction between magnesium and steam
Mg (s) + H2O (g) —> MgO (s) + H2 (g)
Give the formula of the following compounds
1) Limestone
2) quicklime
3) slaked lime
4) lime water
1) CaCO3 (s)
2) CaO (s)
3) Ca(OH)2 (s)
4) Ca(OH)2 (aq)
1) Down group 2 the solubility of the hydroxides …
2) magnesium hydroxide is hardly soluble and can be observed as a …
1) increases, the ionic radius of the group 2 ions (2+) increases down the group. This leads to weaker attraction between the group 2 ion and the hydroxide ion therefore less energy is required to seperate the ions making solubility increases down the group
white precipitate forms
Why is magnesium hydroxide not a dangerous powerful base?
because is solubility is very low
Magnesium hydroxide is used to treat
heartburn because it is base strong enough to neutralise the pH of the stomach bcs it’s very low solubility means it’s not strong enough to damage the body
Calcium hydroxide had the chemical formula Ca(OH)2 and is also known as
slaked lime
Complete the equation
Ca(OH)2 + 2HCl —>
CaCl2 + 2H2O
What do farmers use to neutralise the pH of soul that is too acidic
slaked lime or calcium hydroxide
What is a sulfate
SO4 is a sulfate
what are the group 2 sulfate?
BeSO4 MgSO4 CaSO4 SrSO4 BaSO4 RaSO4
As we go down a group?
The solubility of groups 2 sulfate decreases
the solubility of group 2 hydroxides increases
Some sulfate are almost insoluble in water like what
barium sulfate (exam) radium is the moet insuline sulfate on the periodic table
Barium sulfate is used in x-rays of the digestive system because it is
dense enough to absorb x rays
and insoluble enough to be safe to eat
Barium chloride is used to test for
sulfate ions
what happens if sulfate ions are present
barium sulfate will form which can be observed as a white precipitate due to its very low solubility
Acid is first removed from
carbonate ions which would otherwise also form a white precipitate with the barium
