Periodicity

• How are elements classified in the periodic table?


  Elements are classified as s, p, or d block based on the orbitals of their highest energy electrons.
• What is the trend in atomic radius across a period?


  • Atomic radii decrease from left to right across a period.
  • Increased protons create more positive charge attraction for electrons.
  • Electrons are in the same shell with similar shielding.
• What is the trend in first ionisation energy across a period?


  • There is a general increase in first ionisation energy across a period.
  • This is due to the increasing number of protons while electrons are added to the same shell.
• Why is there a drop in first ionisation energy between Mg and Al?


  Mg has its outer electrons in the 3s subshell, while Al starts filling the 3p subshell, making Al's electron easier to remove.
• What causes the drop in first ionisation energy between phosphorus and sulfur?


  Sulfur's outer electron is paired with another electron in the same 3p orbital, causing slight repulsion and making it easier to remove.
• What are the melting and boiling points trends for Na, Mg, and Al?


  • Na, Mg, Al exhibit metallic bonding.
  • Stronger bonding occurs with more outer shell electrons released to the sea of electrons.
  • Smaller ions with greater positive charge lead to stronger bonding.
• How does silicon's bonding affect its melting and boiling points?


  • Silicon is macromolecular with many strong covalent bonds.
  • High energy is needed to break these covalent bonds, resulting in very high melting and boiling points.
• What type of bonding do Cl2, S8, and P4 exhibit, and how does it affect their melting and boiling points?


  • Cl2 (g), S8 (s), P4 (s) are simple molecular with weak van der Waals forces.
  • Little energy is needed to break these forces, resulting in low melting and boiling points.
• Why does S8 have a higher melting point than P4?


  S8 has more electrons than P4, leading to stronger van der Waals forces between molecules.
• What type of bonding does argon exhibit and how does it affect its melting point?


  • Argon is monoatomic with weak van der Waals forces between atoms.
  • This results in a very low melting point.
• What is periodicity in chemistry?


  • Periodicity is the repeating pattern of physical or chemical properties.
  • It occurs across the periods of the periodic table.
• What are the trends in period 2 compared to period 3 regarding atomic radius and ionization energy?


  • Similar trends in atomic radius and ionization energy are observed in both periods.
  • Drops occur between Be & B and N to O for similar reasons.
• What types of bonding are present in period 2 elements?


  • Li, Be exhibit metallic bonding (high melting points).
  • B, C are macromolecular (very high melting points).
  • N2, O2 are molecular gases (low melting points).
  • Ne is a monoatomic gas (very low melting point).