Periodicity

• What does the Periodic Table arrange elements according to?

  Proton number
• What do all elements along a period have in common?

  They have the same number of electron shells
• What do all elements down a group have in common?

  They have the same number of outer electrons
• How are elements classified in the Periodic Table?

  Into blocks based on electron configuration
• What are the different blocks in the Periodic Table and their corresponding groups?

  • s-block: groups 1 and 2
  • p-block: groups 3 to 0
  • d-block: transition metals
  • f-block: radioactive elements
• What is periodicity in the context of the Periodic Table?

  It is the study of trends linked to different electron configurations
• What happens to atomic radius along a period?

  It decreases
• Why does atomic radius decrease along a period?

  Due to increased nuclear charge for the same number of electron shells
• What happens to atomic radius down a group?

  It increases
• Why does atomic radius increase down a group?

  Because an electron shell is added each time, increasing distance from the nucleus
• What is the effect of electron shielding on atomic radius?

  It reduces nuclear attraction, leading to an increase in atomic radius
• What happens to ionisation energy along a period?

  It increases
• Why does ionisation energy increase along a period?

  Because outer electrons are held more strongly due to decreasing atomic radius and increasing nuclear charge
• What happens to ionisation energy down a group?

  It decreases
• Why does ionisation energy decrease down a group?

  Because nuclear attraction reduces and electron shielding increases
• How are the melting points of Period 3 elements linked to their bond strength and structure?

  • Sodium, magnesium, and aluminium: metallic bonding, melting points increase due to greater positive charged ions.
  • Silicon: macromolecular structure, very high melting point due to strong covalent bonds.
  • Phosphorus, sulphur, and chlorine: simple covalent molecules, low melting points due to weak van der Waals forces.
  • Argon: noble gas, very low melting point due to weak van der Waals forces between individual atoms.

  
• What type of bonding do sodium, magnesium, and aluminium exhibit?

  Metallic bonding
• Why do sodium, magnesium, and aluminium have increasing melting points?

  Due to greater positive charged ions and more free electrons

  
• What type of structure does silicon have?

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

  Because it has a strong covalent structure that requires a lot of energy to break
• What type of molecules are phosphorus, sulphur, and chlorine?

  Simple covalent molecules
• Why do phosphorus, sulphur, and chlorine have relatively low melting points?

  Because they are held together by weak van der Waals forces
• What is the state of argon at room temperature?

  It exists as a gas
• Why does argon have a very low melting point?

  Because it has weak van der Waals forces between individual atoms