Chem 18 Module 1.3: Electronic Structure of the Atom and Atomic
Properties
Periodic Trends
Periodicity- The elements in the periodic table are so arranged that their
properties are periodic functions of their atomic numbers.
The Modern Periodic Law: The chemical properties of the elements are
periodic functions of their atomic numbers.
Effective Nuclear Charge
Zeff = Z -
where:
Z = nuclear charge (atomic number, number of protons)
= shielding constant / Inner (core) electrons / Noble gas
Remember:
Valence electrons- outer elec trons
Core electrons - inner electrons
Effective nuclear charge (Zeff)
dictates the trends in the Periodic Table
high Zeff, stronger attraction of nucleus to the electrons
the “positive charge” felt by an electron
