Properties Of Period 3 Elements And Their Oxides Flashcards
What kind of reactions do period 3 elements under go?
All under go redox reactions except argon (noble gas)
What happens when sodium reacts with water?
Reacts spontaneously
2Na + H2O ——> 2NaOH + H2
Reaction is very fast
The sodium melts due to the heat released and effervescence that is formed from the hydrogen released
Forms a strong alkali of NaOH
What happens when magnesium is reacted with water?
Spontaneous reaction
Mg + 2H2O ——> Mg(OH)2 + H2
Reacts very slowly forming only a few bubbles of hydrogen gas over a few days
However magnesium reacts quickly with steam producing magnesium oxide instead (MgO)
What happens when a period 3 element reacts with oxygen?
Forms an oxide (except argon)
Happens when reacted with oxygen and heated
What are the oxides formed and the observations made with period 3 elements?
Sodium:
NaO2(s)
Yellow flame/ white solid formed
Magnesium:
MgO
Bright white flame / white powder
Aluminium:
Al2O3
Burns brightly / white solid forms
Silicon:
SiO2
Quartz (silicon dioxide)
Phosphorous:
P4O10 (excess O2) / P2O3 ( limited O2)
Red phosphorus must be heated/ white ignites spontaneously
Sulphur:
SO2 / SO3
Blue flame
What is the bonding like in the period 3 oxides?
Na2O ——> Al2O3
Ionic bonding and giant ionic structures
SiO2 covalent bonding and s giant covalent structure
P4O10 ——> SO3
Covalent bonding and molecular structure
What is the trend in bonding across the period 3?
Changes from purely ionic to purely covalent
What is the trend in melting points for period 3 elements?
Ionic structure have highest melting points
But Al2O3 has a high degree of covalent and therefore has a Lower melting point or other ionic elements
Molecular structures have a decreasing trend as the size and strength of van der waals decreases
What happens when magnesium and sodium oxide react with water?
MgO and Na2O are almost completely ionic and so hydration reactions occur.
They form basic solutions which react with acids
What happens when aluminium and silicon oxide react with water?
Aluminium oxide and silicon oxide are insoluble and hence do not react with water
What happens when the non metal oxides of period 3 react with water?
Forms acidic solutions which react with bases
What happens when aluminium oxide is added to an acid or a base?
It will react with both as aluminium oxide is amphoteric and so can act as an acid or base
Why is silicon oxide an acidic oxide? explain using an equation.
Non metal oxide and hence forms acidic solutions which react with bases.
SiO2 + 2NaOH —-> SiNa2O3 + H2O
why is the melting point of sulphur oxide lower than phosphorous oxide?
SO2 is a smaller molecule and hence has a lower Mr and surface area so the molecule is less polarisable.
Explain why common oxides of Aluminium are insoluble in water?
Aluminium oxide is ionic, and therefore has a high lattice enthalpy of dissociation. the enthalpies of hydration do not compensate and hence mean aluminium oxide is insoluble.
