Unit 1.6

• Periodic table


  Arranges the elements according to increasing atomic number
• Groups


  • Vertical columns, all elements have the same outer electron configuration, group number indicates number of electrons in outer shell
• Periods


  • Horizontal rows, all elements have the same number of electron shells
• 1. block


  Groups 1 and 2, elements have outer electrons in s orbital
• 1. block


  Groups 3 to 8, elements have outer electrons in p orbital
• 1. block


  Elements between Groups 2 and 3, elements have outer electrons in d orbital
• Metals are on the left and middle of the periodic table, non-metals are on the right
• Ionisation energy


  • Increases across a period, decreases between Group 2 and 3, decreases between Group 5 and 6
• Electronegativity


  • Increases across a period, decreases down a group
• Melting and boiling temperatures

  1. Increase from first to fourth element in a period, large decrease at fifth element, small general decrease to eighth element

  2. Changes in structure from metallic to giant covalent to simple molecular
• Reduction and oxidation (redox)

  Reduction is gain of electrons, oxidation is loss of electrons
• Oxidation number increases if species is oxidised, decreases if species is reduced</b>
• Group 1 metals


  • React vigorously with cold water, reactivity increases down the group
• Group 2 metals


  • React less vigorously with water, reactivity increases down the group
• Magnesium reacts with steam to produce oxide and hydrogen
• Reactivity of s-block metals

  • Increases down a group as ionisation energy decreases, Group 1 more reactive than Group 2
• Reaction with acids


  • Group 2 metals react vigorously with hydrochloric acid, reactivity increases down the group, only magnesium reacts with sulfuric acid
• Reaction with oxygen


  • Group 2 metals (except magnesium) burn with characteristic flame to form solid white oxides, Group 1 metals also form white solids and burn with characteristic flame
• Metal oxides


  • Basic, non-metal oxides are acidic
• Group 1 and barium oxides

  • React with water to form soluble hydroxides (alkalis)
• Other Group 2 hydroxides

  • Not very soluble, only weakly basic
• 1. block elements (except Mg) can be identified by flame test
• Reaction with oxygen


  2Mg+O₂ <-2MgO
• Group 2 metals


  • Apart from magnesium, all tend to burn with a characteristic flame
  • Burn to form solid white oxides
• Group 1 metals


  • Also form white solids and burn with a characteristic flame
• Group 1 metals also form peroxides and superoxides but you do not need to know about these in this course
• Reaction of Group 1 oxides and barium oxide with water

  Form a soluble hydroxide
• Hydroxides


  Alkalis (since they are soluble)
• Other Group 2 hydroxides

  Not very soluble, so saturated solutions are only weakly basic
• Flame test for Group 2 (except Mg) and Group 1 elements


  Moistened metal wire/splint dipped in compound and held in Bunsen flame
• Characteristic flame colours


  • Red (Li)
  • Orange-yellow (Na)
  • Crimson (K)
  • Apple green (Ba)
• All Group 1 compounds are soluble. Many Group 2 compounds are not
• Solubility trends for Group 2 compounds


  • Nitrates are soluble
  • Carbonates are insoluble
  • Hydroxides become more soluble down the group
  • Sulfates become less soluble down the group
• All the precipitates are white
• Thermal decomposition of Group 2 hydroxides

  Decompose on heating to the oxide and steam
• Thermal decomposition of Group 2 carbonates

  Decompose on heating to the oxide and carbon dioxide
• Thermal stability of Group 2 hydroxides and carbonates increases down the group
• Halogens


  Elements that form salts called halides
• Halogens


  • Form diatomic molecules with a single covalent bond
  • Increase in induced dipole-induced dipole intermolecular forces down the group, leading to increased melting and boiling points
  • Reactivity and oxidising power decrease down the group
• Halogen reactions with metals

  1. React directly to form halides

  2. Iron reacts to form iron(III) halide with bromine, but only iron(II) halide with iodine