Oxidation and reduction

• G2 reaction with water

  X + 2H2O = X(OH)2 + H2
• Group 2 reactivity in water

  Increases as you go down, shielding and atomic radius increase causing weak electrostatic attractions making it easier to lose electrons
• Solubility in sulfates

  Less soluble as you go down
• Solubility in hydroxides


  More soluble as you go down
• Atomic radius


  • Increases more as element has more orbitals creating a larger atomic radius
• Atomic radius


  • Increases more as element has more orbitals creating a larger atomic radius
• Electronegativity


  Decreases as you get further from the nucleus, meaning it decreases more with increased shielding and greater atomic radius
• 1st ionisation energy


  Decreases more with increased shielding and greater atomic radius, making it more difficult to gain electrons
• Melting point


  Decreases more with increased number of electrons causing a stronger attraction between the nucleus and electrons, meaning more energy is needed to overcome the forces between ions
• Melting point between Mg and Ca

  Increases and then slowly decreases
• Extracting titanium from its ore

  1. TiO2 + 2C + Cl2 -> TiCl4 + 2CO

  2. TiCl4 + 2Mg -> Ti + 2MgCl2
• Barium uses


  • Barium meal, highlights digestive system in X-ray
• Magnesium uses

  • Magnesium- extracting titanium form ore
  • Mg(OH)2- indigestion remedy
• Calcium uses

  • Ca(OH)2- corrects soil PH
  • CaO- flue gas desulfurisation
  • CaCO3- indigestion remedy
• Disproportionation 


  Same species is oxidised and reduced
• What is an oxidation number?

  The number of electrons an atom uses to bond with any other atom
• What is the oxidation number of an uncombined element such as C, H, O2?

  0
• What is the oxidation number of combined oxygen such as in H2O?


  • 2
• What is the oxidation number of oxygen in peroxides?

  • 1
• What is the oxidation number of combined hydrogen such as in NH3, H2S?

  +1
• What is the oxidation number of hydrogen in metal hydrides such as LiH?

  • 1
• What is the oxidation number of a simple ion?

  Charge on the ion
• How is the oxidation number of a simple ion represented with an example?

  1. g., Na+ → +1; Cl- → -1
• What is the oxidation number of combined fluorine such as in NaF, CaF2?

  • 1
• How is an element with more than one stable oxidation number indicated?

  Written as a Roman numeral
• What is the oxidation number of Fe in iron (III) chloride?

  +3
• What are oxyanions?

  Negative ions that have an element along with oxygen
• What is the oxidation number of S in SO4$^{2-}$?


  +6
• How is the oxidation number of S in SO4$^{2-}$ calculated?


  Combined oxygen has an oxidation number of -2; 4 x -2 = -8; the charge is -2, so sum must equal -2.
• Define oxidation in terms of electron transfer and oxidation number.

  Oxidation is the loss of electrons and an increase in oxidation number.
• Define reduction in terms of electron transfer and oxidation number.

  Reduction is the gain of electrons and a decrease in oxidation number.
• What is a redox reaction?

  A reaction in which both oxidation and reduction takes place.
• What is the oxidation number of a metal?

  0, because it is an uncombined element.