ATOMIC RADIUS

• • Atomic Radius: The distance from the nucleus to the outermost electron shell of an atom. It is a measure of the size of an atom.
  • Trend:
  • Across a Period: Atomic radius decreases as you move left to right across a period because of increasing nuclear charge, which pulls electrons closer.
  • Down a Group: Atomic radius increases as you move down a group due to additional electron shells.
  • Explanation: electron shielding and effective nuclear charge influence atomic size.
  • Examples: Compare atomic radii for elements like Li, Na, K (down a group) and C, N, O (across a period).
• Atomic radius increases down a group?

  Yes, it does!
• Atomic radius decreases across a period?

  Yes, it does!
• Why does atomic radius increase down a group?

  More energy levels, electrons farther away, and valence shell increases!
• Noble gases


  Exceptions to the trend: full outer energy level, stable, and compact arrangement of electrons; smaller atomic radius
• What happens to the atomic radius as we move down a group in the periodic table?

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

  Each element has an additional energy level
• How does the addition of energy levels affect atomic size?

  It makes the atom larger
• What role do inner electrons play in atomic size?

  They shield outer electrons from the nucleus
• How does the increase in nuclear charge relate to atomic radius down a group?

  The effect of added energy levels outweighs nuclear charge
• Compare the atomic radius of lithium and potassium in Group 1.

  • Lithium (Li) has a smaller atomic radius
  • Potassium (K) has a larger atomic radius
  • Potassium has more electron shells than lithium