3.2.2 group 2 - the alkaline earth metals Flashcards
how does 1st ionisation energy change as you go down group 2
decreases
the outer electrons are further away from the nucleus and more shielded. Therefore the attraction from the nucleus is weaker and requires less energy to overcome
how does the atomic radius change going down group 2
gets larger as there are more electrons and more shells
how does melting point change as you go down group 2
generally goes down as the metallic bonding gets weaker due to the increasing size of the metal cations
how does electronegativity change as you go down the group
gets smaller as the electrons in the covalent bonds get further away from the nucleus and get more shielded by extra inner electron shells
what is the trend of the group 2 metals as they react with water
they get more reactive as you go down the group as the valence electrons are further away from the nucleus and more shielded so are more easily lost
general equation for the reaction between group 2 metals and water
M + 2H2O -> M(OH)2 + H2 ( metal + water -> metal hydroxide and hydrogen)
why are the solutions formed when reacting group 2 metals with water alkaline
hydroxide ions are formed
why does the pH of the group 2 hydroxides increase in pH going down the group
there is an increased concentration of aqueous OH- ions due to the solubility of the hydroxides
what happens when magnesium reacts with steam
white solid formed (MgO) with a bright white flame
what happen when sodium reacts with oxygen
burns with a yellow flame and makes a white ppt
what happens when sodium reacts with water
Na floats on the water and there is effervescence. Forms and alkaline and melts into a ball
equation for sodium and water
2Na + 2H2O -> 2NaOH + H2
how does the solubility of group 2 hydroxides change as you go down the group
increases
how does the pH of the group 2 hydroxides change as you go down the group
increases
why does alkalinity of the solutions change as you go down group 2 hydroxides
becomes more alkaline and pH increases as they get more soluble as you go down so there is an increased concentration of OH- ions
what is the trend in solubility of group 2 sulphates as you go down the group
solubility decreases
one use of barium sulphate that relies on its insoluble nature
used in barium meals for the aiding of the diagnosis of the gastro-intestinal tract. Barium sulphate is drank as a suspension that coats the tract and acts as a contrast medium that highlights any abnormality of the soft tissue
what is the chemical test for sulphates
add a mixture of BaCl2 and HCl to the unknown solution. If the unknown is a sulphate, it form a white ppt of BaSO4
why is HCl also used as well as barium chloride solution when testing for sulphates
prevents the formation of unwanted ppts
what is a base
reacts with an acid to give salt and water
what is milk of magnesia
an antacid containing a suspension of magnesium hydroxide
what is a suspension
small particles of an insoluble solid suspended in a liquid
why does magnesium hydroxide forma suspension and not a solution
Mg(OH)2 is insoluble in water
why does magnesium hydroxide relieve indigestion
it is a base and reacts with excess stomach acid to neutralise it
what group 2 hydroxide is used to treat acidic soils
Calcium hydroxide
what acidic gas is produced when sulphur in fossil fuels is burnt
sulphur dioxide (acid rain)
why is titanium so expensive
mg is used to extract it using electrolysis and mg is expensive
