Structure 3.1

• Group: vertical colum
• Period: horizontal row
• group: valence shells
• Period: energy level occupied
• Period number = principal quantum number
• The arrangement revealed periodic trends and helped in predicting properties due to the gap
• metals: SOild at room temp (22c), malleable & ductile, high electrical conductivity, high density, low ionisation energy, low electronegativity, metallic lustre.
• non-metals: gases or liquids at room temp, brittle, poor electrical conductors, low densities, high ionisation energies, high electronegativities, no metallic lustre.
• Metalloids: have some characteristics of metals and non-metals
• Metalloids: solid at room temp, some metallic lustre, brittle, intermediate conductivity, moderate density.
• Periodicity: after certain regular but varying intervals, the chemical elements show an approximate repetition in their property
• Periodicity in properties of elements

  The periodicity of:

  1. atomic radius, 
  2. ionic radius, 
  3. ionization energy, 
  4. electron affinity and 
  5. electronegativity
• First Electron affinity decreases in group one. (become less exothermic)
• group 16: first electron is exothermic and second is endothermic
• group 16: electron affinity decreases down a group
• fluorine has a lower electron affinity than chlorine due to its very small atomic radius which causes replusion
• electron negativity: measure of the attraction of an atom for bonding pairs of electrons
• Metallic charcter: how easily an atom can lose electrons
• Metallic elements: low ionisation energy due to the lost of electrons.
• Non-metallic: higher ionisation energy due to gain of electron
• group 18: the halogens are the least reactive since they have a full valence shell
• Group one: General charcterstics: silvery soft metal, to reactive to be found in nature, is often stored in oil, easily forms a single charged ion
• Physical group one properties: good conductores of heat and electricity, low in density, shiny grey surface,cut like butter with knife.
• chemical properties of group one: very reactive, form ionic compounds with non-metal
• group 17: easily accept an electron, strong pull from nucleus of the halogen to the electrons in the neighbouring atoms
• Group one, general charcteristics: low 1st ionization, reactivity increases down a group, ability to conduct electricity and heat due to the mobility of their valence electron.
• Group 17: more soluble ( nonpolar solvent) less soluble (polar solvents like water)
• Halogens: Cl 2, Br 2, I 2
• Helide: Cl -, Br -, I -
• Difference betweem halogen and helide: Coloured gas, Increase melting and boiling points, increase down a group due to increase molar mass and decrease in reacitvity
• Group 1 and 2: basic acid-base properties (period 3: NaO, MgO)
• Group 13: amphoteric acid and base properties (Period Al2O3)
• Group 14,15,16,17: Acid and base properties: Acidic
• Basic Oxides and metallic: Na2O + H2O --> 2NaOH

  MgO + H2O --> Mg(OH)2

  PH will increase
• Acid Oxides: SO3 + H2O --> H2SO4

  P4O10 + 6H2O -->4H3PO4

  3NO2 + H2O --> 2HNO3 + NO
• Structure, group 1, group 2 and group 13: Ionic and lattice. (repeating)

  Period 3 example ( Na2O, MgO,Al2O3)
• Group 14 structure: Giant Covalent (mix of iconic and Molecular)

  Period 3 example: SiO2
• Group 15,16,17, molecular Covelent structure: singular

  Period 3 example: (P4O10, P4O6, SO3,SO2,Cl2O1, Cl2O)
• Non-metallic oxide (Acidic): H2O(l) + CO2 (g) ⇌ H2CO3 (aq)

  Carbon Dioxide in water to make carbonic acid weak acid,
• Non-metallic oxide (Acidic): SO3(l) + H2O (L) --> H2SO4(aq)

  Sulfur trioxide + water --> Sulfric (VI) Acid