Periodicity

• What does periodicity refer to?

  Repeating patterns of properties in elements
• Why do elements in the same group have similar chemical properties?

  They have the same number of outer-shell electrons
• What happens to atomic radius across Period 3 (Na → Ar)?

  Atomic radius decreases due to increased nuclear charge
• What is the trend in ionisation energy across Period 3?

  Ionisation energy generally increases across Period 3
• Why is there a slight drop in ionisation energy between Group 2 (Mg) and Group 3 (Al)?

  The outer electron in Al is in a higher energy sub-shell
• Why is there a slight drop in ionisation energy between Group 5 (P) and Group 6 (S)?

  Paired electrons in S repel each other, easing removal
• How does electrical conductivity change across Period 3?

  Conductivity decreases from metals to non-metals
• What is the trend in melting and boiling points across Period 3?

  • Metals (Na → Al): Increase due to stronger metallic bonding
  • Si: Very high due to giant covalent structure
  • Non-metals (P → Ar): Decrease due to weaker van der Waals forces
• Why does silicon have a high melting point?

  Silicon has a giant covalent structure with strong bonds
• How do structures of Period 3 elements change across the period?

  • Na, Mg, Al: Metallic bonding (giant metallic structure)
  • Si: Giant covalent structure
  • P, S, Cl, Ar: Simple molecular structures
• What is the general trend in electronegativity across a period?

  Electronegativity increases due to increasing nuclear charge
• Which Period 3 element has the highest first ionisation energy?

  Argon (Ar)
• Why does sodium (Na) have a low melting point compared to magnesium (Mg) and aluminium (Al)?

  Sodium has fewer delocalised electrons and weaker bonding
• What happens to the reactivity of metals across a period?

  Reactivity decreases as ionisation energy increases
• How do the physical states of Period 3 elements differ at room temperature?

  • Na, Mg, Al: Solids (metals)
  • Si: Solid (giant covalent)
  • P, S, Cl: Solids or gases (simple molecules)
  • Ar: Gas
• How does nuclear charge change across a period?

  Nuclear charge increases as protons are added
• Why does shielding not significantly change across a period?

  Electrons are added to the same energy level
• How do melting and boiling points change across a period for metals and non-metals?

  • Metals: Increase due to stronger metallic bonds
  • Non-metals: Decrease due to weaker van der Waals forces
• What factors affect ionisation energy?

  • Nuclear charge
  • Atomic radius
  • Electron shielding
  • Electron repulsion in orbitals
• What type of bonding is present in Na, Mg, and Al?

  Metallic bonding
• What type of bonding is present in silicon (Si)?

  Giant covalent bonding
• What type of bonding is present in phosphorus (P), sulfur (S), and chlorine (Cl)?

  Simple covalent bonding with weak van der Waals forces
• What happens to atomic radius down a group?

  Atomic radius increases due to additional electron shells
• What is the trend in electronegativity down a group?

  Electronegativity decreases due to increased atomic radius
• What is the trend in ionisation energy down a group?

  Ionisation energy decreases due to increased atomic radius
• How does ionisation energy change for successive electrons in an atom?

  Ionisation energy increases for successive electrons removed
• Why do metals (Na, Mg, Al) conduct electricity but non-metals (Si, P, S, Cl, Ar) do not?

  Metals have delocalised electrons that carry charge
• What happens to melting and boiling points across Period 3?

  • Metals (Na → Al): Increase due to stronger metallic bonding
  • Si: High due to giant covalent bonding
  • Non-metals (P → Ar): Decrease due to weak van der Waals forces
• How do atomic radius and electronegativity explain the trend in ionisation energy across a period?

  Decreasing atomic radius and increasing electronegativity explain trends
• Why does sodium (Na) have a low melting point compared to magnesium (Mg) and aluminium (Al)?

  Sodium has fewer delocalised electrons and weaker bonding
• Which Period 3 element has the highest first ionisation energy and why?

  Argon (Ar) has the highest nuclear charge
• How are elements arranged in the Periodic Table?

  According to proton number
• What do all elements in a period have in common?

  Same number of electron shells
• What do all elements in a group have in common?

  Same number of outer electrons
• Which groups are included in the s-block?

  Groups 1 and 2
• Which groups are included in the p-block?

  Groups 3 to 0
• Which elements are included in the d-block?

  Transition metals
• Which elements are included in the f-block?

  Radioactive elements
• What happens to atomic radius along a period?

  Decreases
• Why does atomic radius decrease along a period?

  Increased nuclear charge