3.2.4 Properties of Period 3 Elements and their Oxides and Chlorides Flashcards
Explain why sodium is more reactive than magnesium
- ∵ it takes less energy to lose 1 electron than to lose 2
- ∴ more energy (usually heat) is needed for magnesium to react
Sodium is more reactive than magnesium and this is shown in their reactions with ___
water
Describe how sodium reacts with cold water
- Reacts vigorously
- Forms molten ball on surface
- Fizzing
- Produces H2 gas
Write the equation for when sodium reacts with water
Describe how magnesium react with cold water
- Reacts very slowly
- Forms weakly alkaline solution
- Forms thin coating of magnesium hydroxide forms on surface of the metal
Why is the solution produced from when magnesium reacts with cold water weakly alkaline?
- ∵ magnesium hydroxide is not very soluble in water as its lattice is stronger
- it’s sparingly soluble
- ∴ few hydroxide ions are produced
State the equation for when magnesium reacts with cold water
Describe how magnesium reacts with steam
- Magnesium reacts faster with steam (i.e. when there’s more energy)
- To form magnesium oxide
State the equation for when magnesium reacts with steam
When Period 3 elements react with oxygen, what do they form?
oxides
When Period 3 elements react with oxygen, they are usually oxidised to their _____ oxidation states, same as their _____ _____
When Period 3 elements react with oxygen, they are usually oxidised to their highest oxidation states, same as their group numbers
Reactions with Oxygen
State which Period 3 element isn’t oxidised to their highest oxidation state & state its oxidation state
- Sulfur forms SO₂
- +4 oxidation state
Reactions with Oxygen
Explain why sulfur isn’t oxidised to its highest oxidation state
A high temp. and catalyst is needed to make SO3, where S has oxidation state of +6
More ____ metals (Na, Mg) and _____ (P, S) react readily in air, while ___ and ___ react slowly
More reactive metals (Na, Mg) and non-metals (P, S) react readily in air, while Al and Si react slowly
Na2O, MgO & Al2O3 have ____ melting points
high
Explain why Na2O, MgO & Al2O3 have high melting points
- Giant ionic lattices
- Strong forces of attraction between ions = lots of energy needed to break bonds
MgO has a ____ melting point than Na2O
higher
Why does MgO have a higher melting point than Na2O?
- Mg forms 2+ ions
- So bonds more strongly than 1+ Na ions in Na2O
Al2O3 has a ____ melting point than MgO
lower
Why does Al2O3 have a lower melting point than MgO?
- ∵ of difference in electronegativity between Al and O isn’t as large as between Mg and O
- Means oxygen ions in Al2O3 don’t attract electrons in metal-oxygen bond as strongly MgO
- Makes bonds in Al2O3 partially covalent
SiO2 has a _____ melting point than non-metal oxides
higher
Why does SiO2 have a higher melting point than non-metal oxides
- ∵ has giant macromolecular structure
- Have to break strong covalent bonds = lots of energy
Why does P4O10 and SO2 have low melting points?
- ∵ form simple molecular structure
- Have weak intermolecular forces (dipole-dipole and van der Waals)
- Take little energy to break
State the equation for when sodium and oxygen react, include state symbols
State the equation for when aluminium and oxygen react, include state symbols
State the equation for when phosphorus and oxygen react, include state symbols.
State the equation for when magnesium and oxygen react, include state symbols
State the equation for when silicon and oxygen react, include state symbols
State the equation for when sulfur and oxygen react, include state symbols
Ionic Oxides are _____
Alkaline
Covalent Oxides are ____
Acidic
Explain why ionic oxides are alkaline
- Ionic oxides (of Na and Mg) contain oxide ions (O2-)
- When they dissolve in water, O2- ions accept protons from water molecules to form hydroxide ions
Explain why the ionic oxides of Na are more alkaline than those for Mg
Sodium hydroxide is more soluble in water ∴ more alkaline solution than magnesium hydroxide