Properties of Period 3 elements and their oxides Flashcards
how do Na and Mg react?
both react ionically to form positive ions
which is more reactive, Na or Mg, and why?
Na is more reactive than Mg because it only has to lose one electron (whereas Mg has to lose two) so less energy is required to ionise it
what do the period 3 elements react with oxygen to form?
oxides in their highest oxidation state
what are the oxides that form form the period 3 elements:
- phosphorus
- aluminium
P4O10
Al2O3
what is required for sulfur trioxide (SO3) to form?
high temperatures and a catalyst
what affects the reactivity and melting points of the period 3 oxides?
structure and bonding
the reaction of Mg with water
Mg + 2H20 –> Mg(OH)2 + H2
the reaction of Mg with steam
Mg + H20 –> MgO + H2
how does Mg react with water?
very slowly
how does Mg react with steam?
vigorously, burning with a bright white flame
how does Na react with cold water?
vigorously, with lots of fizzing
how do the period 3 elements react in air?
Na, Mg, P and S react readily
Al and Si react slowly
what are Na2O, MgO and Al2O3?
ionic oxides (metal + non-metal)
why does MgO have a higher melting point than Na2O?
the Mg2+ ions are more strongly attracted to the oxygen than the Na+ ions
why do P4O10 and SO2 have low melting points?
they form simple molecular structures held together by VDWs and dipole-dipole forces (weak IMFs)
why does SiO2 have a higher melting point than the other non-metal oxides?
it has a giant macromolecular structure containing strong covalent bonds which require a lot of energy to overcome
why does Al2O3 have a lower than expected melting point?
because there is a smaller difference in electronegativity between Al and O so the oxygen ions don’t attract the electrons in the metal-oxygen bond as strongly as in MgO
what are the bonds in Al2O3?
partially covalent
are covalent oxides alkaline or acidic?
acidic
is Al2O3 soluble in water
no Al2O3 is insoluble in water due to its slight covalent character
acid + base –> ?
acid + base –> salt + water
what does it mean if a compound is amphoteric?
it can react as an acid and as a base
basic oxides neutralise ?
basic oxides neutralise acids
acidic oxides neutralise ?
acidic oxides neutralise bases
amphoteric oxides neutralise ?
amphoteric oxides neutralise acids and bases
do Na2O, MgO and Al2O3 have high or low melting points? why?
high melting points because they form giant ionic lattices
what solutions form when ionic oxides react with water?
alkaline solutions because the O2- ions accept H+ ions from the water molecules to form OH- ions
why is the solution formed when MgO reacts with water less alkaline than when Na2O reacts with water?
Na2O is more soluble in water so more OH- are produced
what do simple covalent oxides form when added to water? why?
acidic solutions because they react to form an acid which then dissociates to release H+ ions
what are P4O10 and SO2?
simple covalent oxides
phosphorus oxide + water –> ?
phosphorus oxide + water –> phosphoric acid (H3PO4)
sulfur dioxide + water –> ?
sulfur dioxide + water –> sulphuric (IV) acid (H2SO3!)
sulfur trioxide + water –> ?
sulfur dioxide + water –> sulphuric acid (VI) (H2SO4!)
how does SiO2 react with water?
SiO2 is insoluble in water because it’s many strong covalent bonds take a lot of energy to overcome
what is SiO2 classed as?
an acid because it will react with a base to form a salt
what is Al2O3 classed as?
amphoteric as t all react with both acids and bases to form a salt
when aluminium oxide is acting as an acid and reacts with a base, no ? is produced
no water is produced - only the salt
