Periodicity

• How are elements classified in the periodic table?

  As s, p, or d block elements
• What determines the classification of elements into s, p, or d blocks?

  According to the orbitals of highest energy electrons
• What happens to atomic radius across a period?

  Atomic radius decreases from left to right
• Why does atomic radius decrease across a period?

  Increased protons create stronger attraction for electrons
• What is the general trend of 1st ionisation energy across a period?

  It generally increases across a period
• Why does 1st ionisation energy increase across a period?

  Due to increasing number of protons in the nucleus
• What causes the drop in ionisation energy between Mg and Al?

  Al has outer electrons in the higher energy 3p subshell
• Why is it easier to remove an electron from sulfur than phosphorus?

  Because sulfur's outer electron is paired, causing repulsion
• What type of bonding do Na, Mg, and Al exhibit?

  Metallic bonding
• How does metallic bonding strength change with more outer electrons?

  It gets stronger with more outer electrons released
• What type of structure does silicon (Si) have?

  Macromolecular structure
• Why does silicon have a very high melting and boiling point?

  Due to many strong covalent bonds between atoms
• What type of bonding do Cl2, S8, and P4 exhibit?

  Simple molecular bonding
• Why do Cl2, S8, and P4 have low melting and boiling points?

  Weak van der Waals forces require little energy to break
• Why does S8 have a higher melting point than P4?

  S8 has more electrons, leading to stronger van der Waals forces
• What type of bonding does argon (Ar) exhibit?

  Monoatomic with weak van der Waals forces
• What is periodicity in the context of the periodic table?

  It is the repeating pattern of properties across periods
• What are the trends in atomic radius, ionisation energy, and melting/boiling points across periods 2 and 3?

  • Atomic radius decreases from left to right
  • 1st ionisation energy generally increases across a period
  • Melting and boiling points vary based on bonding types:
  • Metallic bonding (Na, Mg, Al) has high mp/bp
  • Macromolecular (Si) has very high mp/bp
  • Simple molecular (Cl2, S8, P4) has low mp/bp
  • Monoatomic (Ar) has very low mp/bp
• What are the specific drops in ionisation energy observed in periods 2 and 3?

  • Drop between Be and B due to 2s to 2p transition
  • Drop between N and O due to pairing of electrons in 2p orbital
  • Drop between Mg and Al due to 3s to 3p transition
  • Drop between P and S due to pairing of electrons in 3p orbital