Chapter 22- Periodicity Flashcards
What is the reaction between sodium and water and what are the observations?
2Na (s) + 2H2O (l) —> 2NaOH (aq) + H2 (g)
Vigorous, sodium fizzes on surface
What is the reaction between magnesium and water at room temp?
Mg (s) + 2H2O (l) —> Mg(OH)2 (aq) + H2 (g)
Very slow at RT, few H2 bubbles after days
What is the reaction between magnesium and steam?
Mg (s) + H2O (g) —> MgO (s) + H2 (g)
Violent, burns with bright white flame
How do the reactions between sodium and water and magnesium and water compare?
Both react ionically to form positive ions however Na is more reactive as it loses one electron to form 1+ ions while Mg loses two electrons to form 2+ ions which requires more energy
How do period 3 elements react with oxygen?
React to form oxides with the period 3 element in their highest oxidation state, often their group number
What is the reaction between sodium and oxygen and what are some observations?
2Na (s) + 0.5 O2 (g) –> Na2O (s)
Yellow flame
What is the reaction between magnesium and oxygen and what are some observations?
2Mg (s) + O2 (g) –> 2MgO (s)
Bright white flame
What is the reaction between aluminium and oxygen?
4Al (s) + 3O2 (g) –> 2Al2O3 (s)
What is the reaction between silicon and oxygen?
Si (s) + O2 (g) –> SiO2 (s)
What is the reaction between phosphorus and oxygen and what are some observations?
4P (s) + 5O2 (g) –> P4O10 (s)
White phosphorus spontaneously ignites and white smoke is given off
What is the common reaction between sulfur and oxygen and what are some observations?
S (s) + O2 (g) –> SO2 (g)
Blue flame
What is the other reaction between sulfur and oxygen and what are the conditions?
2S (s) + 3O2 (g) –> 2SO3 (g)
Requires high temperature and a catalyst
What is the structure and bonding of sodium and magnesium oxides?
Giant ionic lattices
Ionic as a metal and non-metal are bonded and there is a large difference in electronegativities
What is the structure and bonding of aluminium oxide?
Ionic with covalent character as a metal and non-metal are bonded however aluminium forms a small ion with high charge (3+) so it is close to the oxide ion and distorts its electron cloud
What is the structure and bonding of silicon oxide?
Giant covalent (macromolecular) structure
Many bonds throughout so high melting point
What is the structure and bonding of phosphorus and sulfur oxides?
Simple covalent structures
Covalent bonds in molecules and weak VdWs and dipole-dipole attractions between the molecules so a lower melting point, hence sulfur oxides being gaseous at RT
What is the general trend in melting points of oxides across period 3 and why is this?
Peaks at MgO then decreases, MgO and Al2O3 are highest due to metal ions with greater charges
What is an alkaline solution?
A solution with a pH of 8-14.
How are alkaline solutions formed from period 3 oxides?
Formed when basic ionic oxides, Na2O or MgO, dissolve in water
The oxide ions accept protons from the water to form OH- ions.
Which are the basic period 3 oxides?
Sodium oxide and magnesium oxide
Which period 3 oxides are insoluble?
Aluminium oxide and silicon dioxide
What is an acidic solution?
Solutions with a pH of 0-6
How are acidic solutions formed from period 3 oxides?
Simple covalent oxides of phosphorus and sulfur react with water and the product dissociates when aqueous, releasing H+ ions
What are the acidic oxides?
Phosphorous oxide and sulfur oxides
What is the reaction between sodium oxide/ magnesium oxide and water and what are the pHs?
Na2O + H2O –> 2NaOH, pH 14
MgO + H2O –> Mg(OH)2, pH 9
What is the reaction between phosphorous oxide and water and what is the resulting pH?
P4O10 (s) + 6H2O (l) –> 4H3PO4 (aq)
When in solution, forms an acid with pH 1-2
What is the reaction between sulfur dioxide and water and what is the resulting pH?
SO2 (g) + H2O (l) –> H2SO3 (aq)
When in solution, forms an acid with pH 2-3
What is the reaction between sulfur trioxide and water and what is the resulting pH?
SO3 (g) + H2O (l) –> H2SO4 (aq)
When in solution, forms an acid with pH 0-1
What is dissocation?
Splitting into ions, ie to produce an acid as a H+ ion and conjugate anion is produced
How do basic, ionic oxides react with acids?
Produce a salt and water in a neutralisation reaction
What is a property of aluminium oxide and why does it have this property?
It is amphoteric meaning it can act as both an acid and an alkali due to it having ionic bonds with covalent character.
How does aluminium oxide react with acids and alkalis?
Reacts to product a salt and water in neutralisation reactions with both
How do the covalent oxides react with bases?
Produce a salt and water in neutralisation reactions
