Periodicity

• How are elements arranged in the periodic table?

  By proton number
• What do groups in the periodic table represent?

  Columns of elements with similar properties
• How many electrons do group one elements have in their outer shell?

  One electron
• What happens to the reactivity of group one elements with water?

  It increases down the group
• What are periods in the periodic table?

  Rows of elements
• What do elements in the same period have in common?

  The same number of electron shells
• What are s-block elements characterized by?

  Electrons in the S orbital
• What happens to atomic radius as we go across period 3?

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

  Increased nuclear charge pulls electrons closer
• What is the effect of shielding on atomic radius?

  It protects inner electrons from the nucleus
• How does atomic radius change down a group?

  It increases
• What is the trend in melting points for metals in period 3?

  Melting points generally increase
• Why does silicon have a high melting point?

  It has a giant covalent structure
• What is the formula for phosphorus?

  P4
• What determines the melting point of phosphorus?

  Weak van der Waals forces
• How does the melting point of sulfur compare to phosphorus?

  Higher due to larger molecular size
• What is the formula for sulfur?

  S8
• Why does chlorine have a lower melting point than sulfur?

  It has smaller van der Waals forces
• What type of structure does argon have?

  Monoatomic
• What is ionization energy?

  Energy to remove one mole of electrons
• What is the first ionization energy of sodium?

  +495.8 kJ/mol
• What is the effect of shielding on ionization energy?

  It decreases the energy required
• How does atomic size affect ionization energy?

  Bigger atoms require less energy to ionize
• What happens to ionization energy as we go down a group?

  It decreases
• What is successive ionization?

  Removing more than one electron from an atom
• What causes the jumps in successive ionization energy?

  Removing electrons from closer shells
• How does ionization energy change across a period?

  It generally increases
• What is the reason for the decrease in ionization energy for aluminum?

  Higher energy subshell further from nucleus
• What causes the decrease in ionization energy for sulfur?

  Electron repulsion in the same subshell
• What are the key concepts related to periodicity?

  • Shielding
  • Nuclear charge
  • Atomic radius
  • Trends in ionization energy
• What are the types of bonding in period 3 elements?

  • Metallic bonding in sodium, magnesium, aluminum
  • Giant covalent structure in silicon
  • Simple molecular structure in phosphorus and sulfur
  • Monoatomic structure in argon
• What are the trends in melting points across period 3?

  • Increase for metals (sodium, magnesium, aluminum)
  • High melting point for silicon (giant covalent)
  • Lower melting points for phosphorus (P4) and sulfur (S8)
  • Lowest for chlorine (Cl2) and argon (monoatomic)
• What are the factors affecting ionization energy?

  • Atomic size
  • Shielding effect
  • Nuclear charge
  • Electron repulsion
• What are the exceptions in ionization energy trends?

  • Decrease in aluminum due to higher energy subshell
  • Decrease in sulfur due to electron repulsion