Period 3 Elements and Oxides Flashcards
Explain why sodium is more reactive than magnesium
Sodium is in group 1 and magnesium is in group 2. When they react, Na loses 1 electron to form 1+ ion, whereas Mg loses 2 electrons to form 2+ ions.
Na is more reactive than Mg as it takes less energy to lose one electron than to lose two.
Therefore, more energy is needed for magnesium to react
Describe sodium reacting with cold water
Product
pH
Reacts vigorously with cold water, forming a molten ball on the surface, fizzing and producing H2 gas.
This produces sodium hydroxide, which is a strongly alkaline solution.
pH 12-14
Describe magnesium reacting with cold water
Product and pH
Why is the solution weakly alkaline?
Reacts very slowly with cold water.
Forms a weak alkaline solution (pH 9-10) and a thin coating of magnesium hydroxide forms on the surface of the metal.
Because magnesium hydroxide is not very soluble in water, so relatively few hydroxide ions are produced
Reaction of magnesium with steam
Mg reacts much faster with steam (ie when there’s more energy) to form magnesium oxide
Period 3 elements and reactivity with oxygen
Describe
Most react readily with oxygen.
Usually oxidised to their highest oxidation states- same as their group numbers
General Equation for Period 3 Elements reacting with oxygen
Element + Oxygen –> Oxide
Equations for reaction of following period 3 elements with oxygen:
Sodium
Magnesium
Aluminium
Silicon
Phosphorous
Sulfur
2Na + 1/2O2 –> Na2O.
Mg + 1/2O2 –> MgO.
2Al + 1 1/2O2 –> Al2O3.
Si + O2 –> SiO2.
P4 + 5O2 –> P4O10.
S + O2 –> SO2
Reaction of Sulfur Dioxide with Oxygen
Forms SO3.
Vanadium catalyst needed
Reactivity with air of Period 3 Elements:
Na
Mg
Al
Si
P
S
Vigorous
Vigorous
Slow
Slow
Spontaneously combusts
Burn steadily
Effect of bonding and structure on the melting point of Na2O , MgO and Al2O3
Metal oxides.
High melting points as they form giant ionic lattices.
Strong forces of attraction between each ion means it takes a lot of heat energy to break the bonds and melt them
Effect of bonding and structure on the melting point of MgO
Higher melting point than Na2O because Mg forms 2+ ions, so bonds more strongly than 1+ Na ions in Na2O
Effect of bonding and structure on the melting point of Al2O3
Lower melting point due to difference in electronegativity between Al and O isn’t as large as between Mg and O.
Means that oxygen ions in Al2O3 don’t attract the electrons in the metal-oxygen bonds as strongly as in MgO.
This makes bonds in Al2O3 partially covalent
Effect of bonding and structure on the melting point of SiO2
Higher melting point than the other non-metal oxides.
Due to its macromolecular structure.
Strong covalent bonds between atoms need to be broken, and this requires a lot of energy
Effect of bonding and structure on the melting point of P4O10 and SO2
Relatively low melting points because they form simple molecular structures.
The molecules are bond by weak intermolecular forces (dipole-dipole and van der Waals) which take little energy to break
Describe ionic oxides
Alkaline
