1.6 - periodic table

• Atomic/Proton number


  The number of protons found in the nucleus of an atom of a particular element
• Cation


  A positively charged ion, e.g. Na+
• Crystallisation


  A preparation technique used to form solid crystals from solution
• Displacement


  A chemical reaction in which one element replaces another element in a compound. A halogen will displace a halide from solution if the halide is below it in the periodic table
• Electronegativity


  The ability of an atom to attract the bonding electrons in a covalent bond. The most electronegative elements (N,O,F) are small and have a relatively high nuclear charge
• Element classification


  An element is classified as s, p, d or f block according to its position in the Periodic Table
• First ionisation energy


  The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions. For example, O(g)→ O+(g) +e-
• Flame test


  An analytical technique used to identify certain elements and ions based on the colour produced when a nichrome wire is dipped into a solution of the species and held in a blue bunsen flame
• Gravimetric analysis


  An analytical technique used to separate ions in a solution
• Ionisation energy trend


  • Ionisation energy generally decreases down the group due to electron shells and shielding increasing. The nucleus, therefore, attracts the outer shell electrons less strongly
• Melting temperature


  The melting point of a substance is the temperature at which it changes from solid state to liquid state
• Melting point trend


  • The Group 7 elements are simple covalent molecules held together with van der waals forces. The strength of these intermolecular forces increases down the group as the relative atomic mass of the molecule increases. Further down the group more energy is required to overcome the van der waals forces, resulting in higher melting points
• Oxidising ability


  Oxidising ability is the ability to act as an oxidising agent. The oxidising ability of the halogens decreases down the group. This is because down the group the atoms get larger so the electrons are less strongly attracted to the nucleus so it is harder to gain an electron
• Oxidation


  Process involving the loss of electrons. Results in an increase in oxidation number
• Oxidising agent


  Electron acceptors. The elements/compounds which accept electrons causing itself to be reduced by oxidising another element/compound
• 1. block element


  Elements in groups 3-8/0 of the periodic table. p-block non-metals generally undergo reduction reactions
• Periodicity


  Trends in element properties with increasing atomic number. The trends are caused by the changes in elements' atomic structure
• Precipitation


  The formation of a solid from a solution
• Reducing ability


  Reducing ability is the ability to act as a reducing agent. The reducing ability, or reducing power, of the halides increases down the group. This is because to act as a reducing agent the halide needs to lose an electron. As you go down the group it is easier for a halide to lose an electron because the attraction from the outer electron and nucleus decreases due to increased shielding and an increasing ionic radius
• Reactivity trend


  • The Group 7 elements need to gain an electron in order to react. As atomic radius increases, this becomes harder as the positive attraction of the nucleus is weakened by additional shielding. Therefore, down Group 7 it is harder to attract an electron so reactivity decreases
• Reducing agent


  Electron donors. The elements/compounds which donate electrons causing itself to be oxidised by reducing another element/compound
• Reduction


  Process involving the gain of electrons. Results in a decrease in oxidation number
• 1. block element


  Elements in Groups 1 and 2 of the periodic table. These generally undergo oxidation reactions
• Solubility


  The ability of a given substance to dissolve in a solvent. Solubility of the Group 2 hydroxides increases down the group and solubility of the Group 2 sulfates decreases down the group
• Test for halide ions


  When combined with acidified silver nitrate, halide ions react to form different coloured precipitates depending on the ion present. The colour of the precipitate formed can be used to identify which halide is present in a solution
• Thermal decomposition


  A reaction in which a chemical substance is broken down by heating
• Thermal stability trend


  • As you go down the period more heat is required for the thermal decomposition of Group 2 nitrates and carbonates because the ions increase in size and therefore have greater thermal stability
• Volatility


  How easily a substance evaporates in standard conditions
• Water treatment


  The addition of chlorine to water to kill bacteria. The risks associated with the use of chlorine to treat water are the hazards of toxic chlorine gas and the possible risks from the formation of chlorinated hydrocarbons
• The Periodic Table


  • Elements are arranged according to atomic number
  • Vertical columns are called groups
  • All elements in the eight main groups contain the same outer electron configuration
  • Horizontal rows are called periods
  • All elements in a period have the same number of quantum shells containing electrons
  • The table is also divided into blocks
  • The name of the block shows the orbital in which the elements' outer electrons lie
• Ionisation energy


  • Generally increases across a period because there is an increase in nuclear charge in the same energy level
  • Decreases between Group 2 and 3 because Group 3's outer electron is partly shielded by the s electrons
  • Decreases between Groups 5 and 6 because of electron-electron repulsion between the electron pair in one p orbital
  • Decreases down a group because the outer electron has increased shielding from inner electrons
• Electronegativity


  Increases across a period because there is an increase in nuclear charge, but the bonding electrons are always shielded by the same inner electrons
• Melting and boiling temperatures


  • Generally increase from the first to the fourth element, followed by a large decrease to the fifth element and a small general decrease to the eighth element
  • This is because the bonding changes from metallic to giant covalent to simple molecular covalent
• Oxidation


  Loss of electrons
• Reduction


  Gain of electrons
• Oxidising agent


  A species that accepts electrons; it becomes reduced itself in the process
• Reducing agent


  A species that donates electrons; it becomes oxidised itself in the process
• Determining if a reaction is redox


  1. Work out the oxidation numbers of the atoms or ions

  2. If the oxidation number increases, the species is oxidised

  3. If the oxidation number decreases, the species is reduced
• Reaction of Group 1 metals with water


  1. React vigorously with cold water to form the hydroxide and hydrogen

  2. The reaction increases in vigour as you go down the group
• Reaction of Group 2 metals with water


  1. React less vigorously

  2. Magnesium reacts very slowly

  3. Calcium produces a steady stream of bubbles and a white precipitate of calcium hydroxide

  4. The hydroxide and hydrogen are formed

  5. The reaction increases as you go down the group