Periodicity

• 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.
• What is the chemical equation for sodium reacting with water?

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

  It reacts very slowly with cold water but more readily with steam.
• What is the equation for magnesium reacting 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?

  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?

  An acidic choking gas (SO2).
• Write the equation for sodium burning in oxygen.

  4 Na (s) + O2 (g) → 2 Na2O (s)
• Write the equation for magnesium burning in oxygen.

  2 Mg (s) + O2 (g) → 2 MgO (s)
• Write the equation for aluminum burning in oxygen.

  4 Al (s) + 3 O2 (g) → 2 Al2O3 (s)
• Write the equation for silicon burning in oxygen.

  Si (s) + O2 (g) → SiO2 (s)
• Write the equation for phosphorus burning in oxygen.

  4 P (s) + 5 O2 (g) → P4O10 (s)
• Write the equation for sulfur burning in oxygen.

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

  • Ionic oxides (Na2O, MgO, Al2O3) have high melting points and ionic giant lattice structures.
  • Macromolecular oxide (SiO2) has very strong covalent bonds and high melting/boiling points.
  • Simple molecular oxides (P4O10, SO2) have weak intermolecular forces and lower melting points.
• Why do ionic oxides have high melting points?

  They have strong forces of attraction between oppositely charged ions.
• What causes the increased melting points from Na to Al in ionic oxides?

  The increased charge on the cation makes the ionic forces stronger.
• What character does Al2O3 exhibit and why?

  It 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.
• Why do P4O10 and SO2 have lower melting points?

  They have weak intermolecular forces between molecules.
• What is the formula for P4O10?

  P4O10 is a molecule containing 4 phosphorus and 10 oxygen atoms.
• How can you experimentally prove that ionic compounds conduct electricity?

  By melting the solids and showing they conduct electricity.
• How does aluminum oxide protect aluminum metal from corrosion?

  It forms a thin layer that is impermeable to air and water.
• Why is sodium stored under oil?

  To prevent it from coming into contact with air.
• What do basic oxides react with to form salts?

  They react with acids.
• Write the equation for sodium oxide reacting with hydrochloric acid.

  Na2O (s) + 2 HCl (aq) → 2 NaCl (aq) + H2O (l)
• Write the equation for magnesium oxide reacting with hydrochloric acid.

  MgO (s) + 2 HCl (aq) → MgCl2 (aq) + H2O (l)
• What is the pattern for acid-base reactions involving oxides?

  Most follow the pattern acid + base → salt + water.
• What is the charge on the phosphate ion?

  PO4^3-
• What is an amphoteric oxide?

  An oxide that can act as both an acid and an alkali.
• Write the equation for aluminum oxide acting as a base.

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

  Al2O3 (s) + 2 NaOH (aq) + 3 H2O (l) → 2 NaAl(OH)4 (aq)
• Why does SiO2 not dissolve in water?

  It has a giant covalent structure with very strong bonds.
• Write the equation for SiO2 reacting with concentrated NaOH.

  2 NaOH (l) + SiO2 (s) → Na2SiO3 (aq) + H2O
• What do the simple molecular acidic oxides react with to form salts?

  They react with bases.
• Write the equation for P4O10 reacting with sodium hydroxide.

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

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

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

  pH 13.