Periodic Trends

Last updated Jun 15, 2023 Edit Source

# ← Chemistry Home

• Video:
• My OneNote page for periodic trends is very informative and has a lot of content
  • Link: Periodic Trends

• Atomic radius is the radius of an atom
  • The distance from the nucleus to the outermost electron shell
• Atomic radius increases down the group but decreases across the period AtomicRadius.png
• Caesium has the biggest atomic radius
• Helium has the smallest atomic radius

• Ionisation energy is the amount of energy needed to remove an electron from an atom
• The smaller an atom is, the harder it is to remove an electron from it
  • Shielding from electrons between the outermost electrons and the nucleus reduce the attractive force of the nucleus
• Ionisation energy is inversely proportional to atomic radius IonisationEnergyTrend.png

• Electronegativity is how much an atom pulls electrons towards itself

  • In a covalent bond between two different elements, the electron density is not shared equally

• $\delta$ is the symbol used to represent electronegativity

  • e.g. H$^{\delta+}$ : O$^{\delta-}$ : H$^{\delta+}$ for a water molecule
    • Oxygen is far more electronegative than the hydrogen atoms

• Electronegativity is inversely proportional to atomic radius ElectronegativityTrend.png

  • However, noble gases do not have electronegativity since they do not want to receive extra electrons due to already being stable
    • Therefore fluorine is the most electronegative atom