CHM 108 SUROVIEC SPRING 2014 Periodic Properties of the Elements

I. Development of the Periodic Table The modern periodic table is credited to Dmitri Mendeleev Table is based on the periodic law

II. Electron Configuration Quantum Mechanical Theory describes the behavior of electrons in atoms.

A. Electron Spin and the Pauli Exclusion Principle Electron configurations can also be represented in an orbital diagram In an orbital diagram the direction of the arrow shows the electron spin

Orbital diagram 1s 1 principal quantum number n angular momentum quantum number l number of electrons in the orbital or subshell Orbital diagram H 1s 1

B. Multi-electron atoms In H and He the energy of the orbital depends only on principle quantum number For atoms with more than 2 electrons, the energy depends on l & n

Example Lithium Magnesium What are the possible quantum numbers for the last (outermost) electron in Cl?

C. Electron configuration of multi-electron atoms Now that we know the energy of orbitals we can build ground state electron configuration for other elements. We use Hund’s rule of filling degenerate orbitals to fill them singly with up spin first

Hund’s Rule

III. Electron Configuration, Valence Electrons and the Periodic Table The highest principle number increases by 1 going down a row As you move across a row the number of electrons increases by 1 in the outer most energy level.

IV. QM Model Explains Ions A all atoms in a column will have the same number of valence electrons

V. Periodic Variations of Physical Properties The chemical and physical properties of elements are a periodic function of atomic number  Recall that the number of electrons is equal to the atomic number of an element  Properties to be considered  Atomic Radius (and Ionic Radius)  Effective Nuclear Charge  Ionization Energy  Electron Affinity

A. Atomic Radius Atomic radius is the average bonding radii between 2 nonbonding atoms

Atomic Radius Trend

B. Effective Nuclear Charge Z eff is the “positive charge” felt by an electron.

B. Effective Nuclear Charge Z (atomic number) Core Electrons Z eff Radius (pm) Na Mg Al Si

VI. Ionic Radius Radius of cations/anions Effects physical and chemical properties of an ionic compound

VI. Ionic Radius

A. Ionization Energy Minimum energy required to remove an electron from a gaseous atom

B. Electron Affinity Measure of how easily an atom will accept an electron

C. Electronegativity An atom’s ability to attract electrons to itself in a chemical bond.