group 2 Flashcards
block group 2 elements are in
s - block
why are group 2 elements in the s - block
highest energy electron occupies an s orbital
physical properties
giant metallic structure
good electrical conductors as they have mobile delocalised electrons which can move and carry a charge
high melting and boiling point as lots of energy is required to break the strong metallic bonds
as a group 2 element loses 2 electrons…
it undergoes oxidation causing reduction
group 2 trends - atomic radii
the atomic radii increases as you go down group 2
there are more shells
more shielding effect by inner shell electrons
increased distance of the outer electron from the nucleus and increased shielding effect far outweigh increase in nuclear charge
nuclear attraction on the outer shell electron decreases down group 2 and this means the atomic radius will increase
group 2 trends - ionisation energy
first ionisation energy decreases as you go down group 2
atomic radius increases
more shells
more shielding effect by inner shell electrons
increased distance of the outer electron from the nucleus and the increased shielding effect far outweigh increase in nuclear charge
nuclear attraction on the outer shell electron decreases
less energy is needed to remove an electron from the outer shell of the group 2 atom and so first ionisation energy decreases
first ionisation energy of Sr
Sr(g) —> Sr+(g) + e-
second ionisation energy of Sr
Sr+ (g) —> Sr 2+ (g) + e-
trend in reactivity down group 2
atomic radius increases
more shells
more shielding effect by inner shell electrons
increased distance of outer electron from the nucleus and increased shielding effect far outweigh increase in nuclear charge
weaker nuclear attraction on the outer shell electrons
ionisation energy decreases
less energy is needed to remove the 2 electrons from the outer shell of the group 2 atom
reactivity decreases down group 2
reaction of group 2 element with oxygen
metal + oxygen —> metal oxide
reaction of group 2 element with water
metal + water —> metal hydroxide + hydrogen
magnesium + steam
magnesium oxide + hydrogen
base
proton acceptors
oxidising agent
reduced
reducing agent
oxidised
metal oxide + water –> metal hydroxide
solubility in group 2
solubility increases down the group
alkalinity in group 2
alkalinity increases down group 2
why does Ba(OH)2 have a greater PH than Ca(OH)2
Ba(OH)2 is more soluble than Ca(OH)2, more ions are released in solution and as concentration of OH- increases, alkalinity increases
Mg(OH)2 use and reason
used in indigestion tablets as an antacid by neutralises HCl
Ca(OH)2 use and reason
used in agriculture to neutralise acid soil by reacting with acid substances in the soil
thermal decomposition
breaking up of a chemical substance with/by heat into at least two chemical substances
thermal decomposition of calcium carbonate
CaCO3 (s) –> CaO (s) + CO2 (g)
decomposition trend in the group
carbonates become more difficult to decompose with heat as yo move down the group so thermal stability increases down the group
why are group 2 elements known as reducing agents
group 2 elements loose 2 electrons so are oxidised themselves and are also electron donors
