Period 3

• How do group 1 metals react with water?

  Vigorously and metal fizzes and floats on water
• What do group 1 metals produce when they react with water?

  Alkaline metal hydroxides and hydrogen gas
• Give an equation for the reaction between Na and H2O.

  2Na (s) + 2H2O (l) --> 2NaOH (aq) + H2 (g)
• How does Mg react with cold water?

  Very slowly
• Give the equation for the reaction between Mg and cold water.

  Mg (s) + 2H2O (aq) --> Mg(OH)2 (aq)+ H2 (g)
• How does Mg react with steam?

  Vigorously
• Give the reaction for Mg with steam.

  Mg (s) + H2O (g) --> MgO (s) + H2 (g)
• What would you observe in a reaction between magnesium and steam?

  Bright white light and white solid formed
• What would you observe in a reaction between magnesium and water?

  Some bubbles of hydrogen and Mg floats to top of water
• Describe the reaction between sodium and oxygen.

  Sodium burns with a yellow flame

  4Na + O2 --> 2Na2O
• Describe how GP2 react with oxygen.

  • Rapidly
  • Metal oxides formed are a solid white powder
  • Mg burns with a bright white flame
  • Reactivity increases down the group due to decreasing ionisation energy
• Give the equation for the reaction of Mg with oxygen.

  2Mg(s) + O2 (g) --> 2MgO (s)
• Is MgO acidic or basic?

  Basic
• Describe how Al reacts with oxygen.

  • Burns with a white flame
  • Produces a white solid
  • 4Al + 3O2 --> 2Al2O3
• Describe how Si reacts with oxygen.


  • Burns with a white flame
  • Forms a white solid
  • Si + O2 -> SiO2
• Describe how P reacts with oxygen.

  • Burns spontaneously with a white flame to form phosphorus oxide in white smoke form
  • P4 + 5O2 --> P4O10
• Describe how sulphur reacts with oxygen.

  • Pale blue flame
  • Colourless sulfur dioxide gas is produced
  • S(g) + O2 (g) --> SO2 (g)
• How can we convert SO2 to SO3?

  • Vanadium pentoxide catalyst at 400-500 degrees and 1-2 atm
  • 2SO2 + O2 --> 2SO3
• Describe the reaction of chlorine with oxygen.

  It does not react directly
• Describe the reaction of oxygen and argon.

  There is no reaction as argon is a noble gas
• Why do Na2O and MgO form ionic lattices?

  Differences in electronegativity
• Why do Na2O and MgO have high MP?

  Strong electrostatic forces of attraction between positive metal nuclei and delocalised electrons
• Why does MgO have a higher melting point than Na2O?

  • Higher nuclear charge on Mg2+ than Na+
  • More protons in the nucleus but same number of shells so a similar shielding effect, atomic radius decreases
  • Electrons are pulled in closer to the nucleus due to stronger forces of attraction
  • Stronger ionic bonds
  • Requires more energy to overcome and break these bonds
• Why does SiO2 have the highest melting point in period three?

  • Giant covalent structure
  • Strong covalent bonds in many directions
  • Requires more energy to overcome
• Why do phosphorus and sulfur form simple covalent molecules?

  smaller difference in electronegativity
• Why does P4O10 have a higher melting point than SO2?

  • Molecules of P4O10 are larger
  • More electrons
  • Greater VDW forces between molecules
• How does sodium oxide react with water?

  Na2O + H2O --> 2NaOH
• How does MgO react with water?

  MgO + H2O --> Mg(OH)2
• Why does Mg(OH)2 solution have a lower pH than NaOH?

  • Mg(OH)2 is only sparingly soluble in water
  • Lower concentration of OH- present in water
• pH of NaOH solution?

  14
• pH of MgO solution?

  9
• Why do Al2O3 and SiO2 form a neutral solution when reacting with water?

  Do not dissolve due to strong ionic lattice and strong macromolecular forces
• Why does Al2O3 have covalent character?

  • Small difference in electronegativity
  • Al3+ has a high charge and is a small ion
  • Oxygen has a high charge and is a large ion
  • Al3+ distorts oxygen electron cloud
• What type of acid is phosphoric acid?

  triprotic
• What shape is H3PO4?

  Tetrahedral
• How does SO2 react with water?

  SO2 + H2O --> H2SO3

  Weak acid is formed

  pH 3
• How does SO3 react with water?

  • SO3 + H2O --> H2SO4
  • pH 0
  • Violent reaction
• What shape is H2SO3?

  Pyramidal
• Reactions of Na2O and HCl

  Na2O + 2HCl --> 2NaCl + H2O
• What do Na2O and MgO react with acid to form?

  Salt and water