Period 3

• Which elements are limited to the reactions with water in this study material?

  Sodium (Na) and Magnesium (Mg)
• What happens when sodium reacts with cold water?


  It fizzes around on the surface and produces sodium hydroxide and hydrogen gas.
• Write the balanced equation for the reaction of sodium with water.

  2 Na (s) + 2 H2O (l) → 2 NaOH (aq) + H2 (g)
• How does magnesium react with cold water compared to steam?

  Magnesium reacts very slowly with cold water but more readily with steam.
• Write the balanced equation for the reaction of magnesium with steam.

  Mg (s) + H2O (g) → MgO (s) + H2 (g)
• What do all the elements Na, Mg, Al, Si, P, and S form when they react with oxygen?

  They all react with oxygen to form oxides.
• What color flame does sodium produce when it burns in oxygen?

  Sodium burns with a yellow flame.
• What is produced when magnesium, aluminum, silicon, and phosphorus burn in oxygen?

  They burn with a white flame to give white solid smoke.
• What gas is produced when sulfur burns in oxygen?

  It produces an acidic choking gas.
• Write the balanced equation for the reaction of sodium with oxygen.

  4 Na (s) + O2 (g) → 2 Na2O (s)
• Write the balanced equation for the reaction of magnesium with oxygen.

  2 Mg (s) + O2 (g) → 2 MgO (s)
• Write the balanced equation for the reaction of aluminum with oxygen.

  4 Al (s) + 3 O2 (g) → 2 Al2O3 (s)
• Write the balanced equation for the reaction of silicon with oxygen.

  Si (s) + O2 (g) → SiO2 (s)
• Write the balanced equation for the reaction of phosphorus with oxygen.

  4 P (s) + 5 O2 (g) → P4O10 (s)
• Write the balanced equation for the reaction of sulfur with oxygen.

  S (s) + O2 (g) → SO2 (g)
• What are the types of oxides formed by Period 3 elements and their properties?

  • Ionic oxides (Na2O, MgO, Al2O3):
  • High melting points
  • Ionic giant lattice structures
  • Strong forces of attraction between oppositely charged ions
  • Macromolecular oxides (SiO2):
  • Very high melting and boiling points due to strong covalent bonds
  • Simple molecular oxides (P4O10, SO2):
  • Lower melting points due to weak intermolecular forces
• Why do ionic oxides have high melting points?

  They have strong forces of attraction between oppositely charged ions in a giant lattice structure.
• What character does Al2O3 exhibit and why?

  Al2O3 is ionic but shows some covalent character due to the smaller aluminum ion being able to distort the oxide charge cloud.
• What is the structure of SiO2?

  SiO2 has a macromolecular structure with many strong covalent bonds.
• What is the behavior of P4O10 and SO2 when they react with bases?

  P4O10 and SO2 react with bases to form salts.
• Write the balanced equation for the reaction of P4O10 with sodium hydroxide.

  P4O10 (s) + 12 NaOH (aq) → 4 Na3PO4 (aq) + 6 H2O (l)
• Write the balanced equation for the reaction of SO2 with sodium hydroxide.

  SO2 (g) + 2 NaOH (aq) → Na2SO3 (aq) + H2O (l)
• Write the balanced equation for the reaction of SO3 with sodium hydroxide.

  SO3 (g) + 2 NaOH (aq) → Na2SO4 (aq) + H2O (l)
• What is the pH of the solution formed when Na2O reacts with water?

  The pH is 13, indicating a vigorous exothermic reaction.
• Why do Al2O3 and SiO2 not dissolve in water?

  They do not dissolve due to the high strength of the Al2O3 ionic lattice and the SiO2 macromolecular structure.
• What happens when P4O10 reacts with water?

  It produces phosphoric acid with a pH of 0.
• What is the trend in behavior of ionic metal oxides and non-metal covalent oxides across Period 3?

  Ionic metal oxides show basic behavior while non-metal covalent oxides show acidic behavior.
• How does aluminum oxide behave in acid-base reactions?

  Aluminum oxide can act as both an acid and an alkali, making it amphoteric.
• Write the balanced equation for aluminum oxide acting as a base.

  Al2O3 (s) + 3 H2SO4 (aq) → Al2(SO4)3 (aq) + 3 H2O (l)
• Write the balanced equation for aluminum oxide acting as an acid.

  Al2O3 (s) + 2 NaOH (aq) + 3 H2O (l) → 2 NaAl(OH)4 (aq)
• What is the reaction of SiO2 with concentrated NaOH?

  SiO2 reacts with very concentrated NaOH to form sodium silicate.
• What is the significance of the reactions of oxides with water in terms of pH changes?

  Metal ionic oxides form alkaline solutions, while non-metal covalent oxides form acidic solutions.
• Why is MgO preferred over NaOH for treating acid in rivers and the stomach?

  MgO is sparingly soluble and weakly alkaline, preventing excessive alkalinity.
• What ions are formed when SO2 and SO3 react with water?

  SO2 forms HSO3⁻ and SO3 forms HSO4²⁻.
• What is the displayed formula for sulfuric acid?

  H2SO4
• What is the displayed formula for sulfurous acid?

  H2SO3
• What is the displayed formula for phosphoric acid?

  H3PO4
• What is the general pattern for acid-base reactions involving Period 3 oxides?

  Most follow the pattern acid + base → salt + water.
• What are the charges on the sulfate and phosphate ions?

  Sulfate has a charge of 2⁻ and phosphate has a charge of 3⁻.
• What is the significance of learning the equations for the reactions of Period 3 oxides?

  It helps in understanding the behavior of these oxides in acid-base reactions.