1. periodicity

• How are elements arranged in the periodic table?

  By proton number, not mass number
• What do groups in the periodic table represent?

  Columns of elements
• 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?

  They react violently, increasing down the group
• What do elements in the same period have in common?

  They have the same number of electron shells
• What are periods in the periodic table?

  Rows of elements
• What are the four blocks of elements in the periodic table?

  S, P, D, and F blocks
• What happens to atomic radius as you go across period 3?

  It decreases
• What happens to atomic radius as you go down a group?

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

  Extra electron shells are added
• What is the trend in melting points for metals in period 3?

  They generally increase
• Why does magnesium have a higher melting point than sodium?

  Magnesium has a higher positive charge
• What type of structure does silicon have?

  Giant covalent structure
• What determines the melting point of phosphorus?

  Van der Waals forces
• Why does sulfur have a higher melting point than phosphorus?

  It has larger Van der Waals forces
• What is the melting point of chlorine compared to sulfur?

  Chlorine has a lower melting point
• What is ionization energy?

  Energy required to remove an electron
• What is the trend in ionization energy across a period?

  It generally increases
• What effect does shielding have on ionization energy?

  More shielding means less energy required
• What happens to ionization energy as you go down a group?

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

  Outer electrons are further from the nucleus
• What is successive ionization?

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

  Removing electrons from shells closer to the nucleus
• What is the significance of the subshell theory?

  It explains ionization energy trends across periods
• Why does aluminum have lower ionization energy than magnesium?

  Its outer electron is in a higher energy subshell
• What causes the decrease in ionization energy for sulfur?

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

  • Shielding
  • Nuclear charge
  • Atomic radius
  • Trends in ionization energy
• What are the trends in melting points across period 3?

  1. Sodium, magnesium, aluminum: increase
  2. Silicon: much higher due to covalent bonds
  3. Phosphorus: lower due to Van der Waals forces
  4. Sulfur: higher than phosphorus due to larger molecules
  5. Chlorine: lower due to smaller molecules
  6. Argon: lowest, monoatomic
• What factors affect ionization energy?

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

  • Aluminum: lower than magnesium due to subshell
  • Sulfur: lower than phosphorus due to electron repulsion