Periodic trends

• Electron shielding is the effect that inner shell electrons have on outer shell electrons, reducing their attraction to the nucleus.
• Group 1 metals (Alkali metals):

  • Form +1 ions
  • Soft and easy to cut
  • Have low melting point
  • Less dense than water (float)
  • React with water to produce metal hydroxide (alkali) and H2
  • Stored in oil to prevent reaction with oxygen and moisture in air
  • Form colorless soluble salts in water
  • Reactivity increases down Group 1, with Francium (Fr) being the most reactive due to its larger atomic radius and the valence electron being furthest away from the nucleus
• • Melting and boiling points decrease down Group 1 due to weaker electrostatic forces of attraction between positive metal ions and sea of localized electrons
• Group 17 non-metals (Halogens):

  • Form -1 ions
  • Form diatomic molecules
  • Color gets darker down Group 17 from F2 (pale yellow gas) to Cl2 (greenish yellow gas) to Br2 (brown liquid) to I2 (purplish black solid)
  • Reactivity decreases down Group 17, with Fluorine (F) being the most reactive due to its small size and strong attractive forces from the nucleus
  • Melting and boiling points increase down Group 17 due to greater intermolecular forces of attraction between bigger molecules
• • Displacement reaction occurs when a more reactive halogen displaces a less reactive halogen from its halide solution
• Group 0 (Noble gases):

  • Have stable duplet or octet electronic structures
  • Prepared by fractional distillation of liquefied air
• Transition metals:

  • High melting and boiling points
  • High density
  • Form colored compounds
  • Have variable oxidation states
• Common ions to remember

  Ag+, Zn2+, Cu2+, Pb2+, Fe2+, Fe3+

  OH-, (NO3)-, (SO4)2-, (CO3)2-,(NH4)+
• Atomic/Ionic Radius Trend:

  • Increases as there are more electron shells and the outer electrons are in an increasingly higher principal energy level, making them further away from the nucleus
  • Atomic size is not affected by nuclear pull due to increased shielding effect from inner electrons
• Atomic/Ionic Radius Trend:

  • Decreases as the number of protons increases, resulting in increased nuclear charge
  • Electrons are more strongly attracted to the nucleus and pulled closer, decreasing atomic radii
• Melting/Boiling Point Trend for Group I Metals:

  • Decrease as more electron shells are added, weakening the electrostatic forces of attraction between positive metal ions and delocalised electrons
• Melting/Boiling Point Trend for Group VII Non-metals (Halogens):

  • Increase as molecules get bigger down the group, leading to greater intermolecular forces of attraction
• Melting/Boiling Point Trend for Sodium, Magnesium, and Aluminium:

  • Metallic bonding with positive metal ions attracted to delocalised electrons
  • Strength of metallic bonding increases from sodium to aluminium due to increased charge on metal ions and number of delocalised electrons
• Melting/Boiling Point Trend for Silicon:

  • Silicon has a giant covalent structure similar to diamond
  • High melting/boiling points due to strong covalent bonds that require a large amount of energy to break
• Melting/Boiling Point Trend for Phosphorus, Sulphur, Chlorine, and Argon:

  • Sulphur has a higher melting/boiling point than the others due to stronger intermolecular forces of attraction between S8 molecules
• First Ionisation Energy Trend for Group I Metals:

  • Decreases as the electron to be removed is further away from the nucleus down the group
• First Ionisation Energy Trend Across Period 3:

  • Increases as there are more protons in each nucleus, leading to increased nuclear charge and attraction between the nucleus and outer electron
• Electronegativity Trend:

  • Decreases for smaller atoms with fewer electron shells due to stronger nuclear pull
  • Increases as the number of protons increases across the period, resulting in a stronger attraction between electrons and the nucleus