periodic table

• hydrogen has one valence electron, helium belongs to group 18, thus it was2 valence electrons
• trend across a period,

  1. no. of proton increases. (number of protons affects the strength of electrostatic FOA between nucleus and electrons
  2. atomic radius decreases ( no. of protons increases while the number of electron shells remain constant, and this leads to stronger traction between nuclei and the valence shells)
  3. metallic properties will decrease(metallic to non metallic, oxides, basic to acidic
• trends down a group

  1. no. of. protons increases
  2. atomic radius increases (down a group, electron shells increase, hence distance between nucleus n valence shells would be greater.
• ion formaton

  • metallic ions usually form cations as they loose their valence electrons to form positively charged ions
  • non metallic elements usually form anions as they gain electrons to form negatively charged ions.
  • elements in the same group generally form ions of the same charge and they form compounds with similar chemical formulae and have similar chemical properties
• group 1. alkali metals

  • g1 elements are alkali metals as they react with water to form alkalis e.g. lithium sodium potassium
  • has 1 electron on v shell, thus charge is +1
• physical properties of g1 metals

  • low mp,bp
  • low densities
  • soft
  • shiny, silvery
  • good conductor of electricity, heat
• trend in g1 physics propertes

  1. mp decreases down the group, weaker electrostatic force of attraction between the metal cations with larger radius and the sea of delocalised valence electrons
  2. densities increase down the grou
• chemical properties of alkali metals

  • reactivity increases down g1 (weaker electrostatic FOA between the nucleus and valence, hence easier for the atom to lose electrons down the group( reactivity))
  • reaction with O2 (alkali metals are very reactive-kept in oil to prevent reaction with air) (g1 metal+O=g1 metal oxide)
  • reaction with water ( react vigorously in cold water to produce metal hydroxide)(g1 metal+h2o=metal hydroxide+hydrogen)
• group 17 halogens

  physical properties

  1. low mp bp
  2. low densities
  3. Br an I are slightly soluble in water
  4. soluble in organic solvent eg oil
• g17 trend in physical properties

  1. mp bp increases as Mr of the halogens increase , resulting in stronger intermolecular FOA which require more energy to overcome during heating
  2. density increase down the group
  3. colour intensity increase down the group
• chemical properties of halogens

  • exist as diatomic covalent molecules
  • have seven valence electrons
  • for covalent compounds by sharing and form their corresponding halide ions by gaining electrons
• reactivity trend g17

  1. decreases down the group9due to weaker electrostatic forces of attraction exerted by nucleus due to larger atomic radii
  2. hence , ability to lose electrons decrease.
• g17

  reaction with metals

  -react vigorously with metals to form ionic salts

  displacement reactioN

  will undergo displacement when more reactive halogen displaces a less reactive halogen
• g18 noble gases

  • unreactive and inert
  • helium has a duplex configuration while the rest have octet configuration
  • exist as monoatomic
  • instead of weak intermolecular, it is weak van der Waal’s forces between atoms
• physical properties g18

  • low densities
  • low mp bp
• trend in physical properties g18

  melting and boiling points increased down the group as atomic mass increased resulting in stronger van der Waal’s forces in return requires more energy to overcome

  densities increase down the group
• trans metals

  physical properties

  • high mp and densities
  • good conductors of both electricity and heat
  • form coloured compounds and solutions
• chemical properties of transition elements

  • commonly used as catalysts as they tend to form ions and compounds e.g iron in the Haber process
  • Ag (+1) Zn(+2)
• Halogen states and colours at RTP:

  • Fluorine- Yellow gas
  • Chlorine- Green gas
  • Bromine- Red brown liquid
  • lodine- Black solid