Periodic Trends

Periodic Trends 1. Atomic Radius 2. Ionization Energy 3. Electronegativity 4. Ionic Radius

Atomic Radius The distance from the center of the nucleus to the outermost valence shell K Na Li Ar Ne

Atomic Radius Periodic Trend Down a group the atomic radius increases Due to the added energy levels Electron shielding: core e- block the attraction between the nucleus and the valence e- Across a period it decreases Due to increased nuclear charge without additional shielding pulls e- in tighter

Ionization Atoms have no (or neutral) charges Ions are charged Charge is caused by adding or losing electrons + charge: loss of electrons - charge: gain of electrons Why does this occur? Stability = full valence shell © 1998 LOGAL

Ionization Energy Ionization Energy: the energy required to remove an electron from the valence shell Why would an electron be removed? Periodic Trend (opposite atomic radii) Down a group I.E. decreases Due to distance from nucleus & electron shielding Across a period it increases Due to increased nuclear charge without additional shielding pulls e- in tighter

Ionization Energy He Ne Ar Li Na K Removal of core electron = BIG IE “Bumps” in graph due to loss of electrons from stable electron configurations He Ne Ar Li Na K

Second and Third Ionization Energy Second I. E.: the energy required to pull the second electron off the same atom Third I.E.: the energy required to pull the third electron off the same atom Would the 2nd & 3rd IE be greater or lesser than the 1st?

Electronegativity Electronegativity: the ability of an atom to attract electrons in a chemical bond Periodic Trend Down a group the electronegativity decreases Due to increasing atomic radii Across a period it increases Due to decreased atomic radii

Ionic Radius The radius of a positive ion is smaller than the atomic radius of its neutral atom Due to loss of electron and often energy level

Ionic Radius The radius of a negative ion is larger than the atomic radius of its neutral atom Due to electron repulsion © 2002 Prentice-Hall, Inc.

Examples Which atom has the larger radii? Be or Ba Ca or Br Which atom has the higher 1st I.E.? N or Bi Ba or Ne Which particle has the larger radius? S or S2- Al or Al3+