properties of period 3 elements Flashcards
reactions of metallic elements with water
sodium
hydrogen gas, effervesence,float,yellow flame
2Na + 2H2O = 2NaOH + H2
magnesium
slower, white powder, bright white light and white flame
steam= Mg + H2O = MgO + h2
WATER = Mg + 2H2O = Mg(OH2)_ + h2
reactions of non-metallic with water
chlorine
dissolves giving very pale green solution
Cl2 + H2O = HCl + HCLO
reactions of metallic elements with oxygen
sodium
burns with yellow flame - produces white powder
4Na + O2 = 2Na2O
magnesium
burns with bright white flame and produces white powder
2Mg + O2 = 2MgO
aluminium
burn with white flame to produce
4Al + 3O2 = 2Al2O3
reactions of non-metal with oxygen
silicon
burns with white flame to produce a white powder
Si + O2 = SiO2
phosphorus
very bright white flame producing a white powder
P4 + 5O2 = P4O10
sulfur
burns with blue flame and gives off choking gas
S + O2 = SO2
what is the overall trend in the melting points of the oxides
increase then decrease
what is the explanation for the melt points of the metallic oxides
high melting points = giant ionic lattice with strong forces of attraction bwt each ion
lots of heat energy required to break the bonds
why does MgO have a higher mp than Na2O
2+ ions attract O2- ion more strongly than 1+ Na atoms
why is Al2O3 mp lower than expected
bc 3+ ions are small with high charge
this distorts oxygen electron cloud making the bond partially covalent
non-metal mp trend
SiO2
highest of non-metals forms a macromolecular structure
strong bonds that require lots of energy to be broken
P4O10 & SO2
simple covalent molecules
weak intermolecular forces that are VDW
why does P4O10 have a larger mp than SO2
much bigger molecule than SO2 =- therefore it has more electrons and so has greater VDW
what are the basic hydroxide metallic oxide reactions with water
Na2O
fast reaction and dissolves into a colourless solution
Na2O + H2O = 2Na+ + 2OH-
ph 14 and ionic lattice
strong alkali
MgO
sparkling soluble so few O2-
MgO + H2O = Mg2+ + 2OH-
weak alkali
what are the insoluble oxides
Al2O3
insoluble therefore no O2- ions
the bonding is too strong so does not react with water
ionic + partial covalent character
ph 7
SiO2
insoluble so therefore no O2- ions
giant = not soluble
ph 7
what are the acidic non-metallic reactions with water
P4O10
violent reaction to give a colourless solution
P4O10 + 6H2O = 4H3PO4 = phosphoric acid
strong acid as fully dissociates into ions
ph 0
SO2 moderately soluble
SO2 + H2O = H2SO3
weak acids only partially dissociates = produces sulphuric (IV) acid or sulfurous acid
ph 3
SO3
SO3 + H2O = H2SO4
strong acid as fully dissociates into sulphuric acid
what is the general ph trend across period 3
alkali to acid
what factors are involved in the reactions of the oxides with water
solubility
chemical trend - the chemical trend is masked by solubility
