Humboldt State University ® Department of Chemistry

Richard A. Paselk

Chem 109 - General Chemistry - Spring 2013

Lecture Notes 22: 15 March

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A Quantum Picture of the Atom, cont.

Let's review where we were last time, keeping in mind all of the calculations and models are actually for hydrogen, but they model larger atoms as has been confirmed with approximate calculations for other atoms.

Electronic Energy Levels:

Atomic Orbitals Supplement More orbitals and some additional explanations.

Quantum Numbers

This is an alternate way of designating the electrons in an atom. Each electron will have a unique set of quantum numbers.

 Quantum Number Symbol Characteristic specified Information provided  Possible values
Principle quantum number n Shell Average distance from nucleus (r) 1, 2, 3, 4, ...
 Angular momentum (Azimuthal) quantum number Subshell Shape of orbital 0, 1, 2, 3, ...n - 1
 Magnetic quantum number  ml Orbital Orientation of orbital - l ... 0 ... +l
Spin quantum number  ms Electron spin  Spin direction ± 1/2

Note that the Pauli exclusion principle and electron spin mean that a maximum of two electrons may occupy a single orbital.

Atomic Structure & Chemical Periodicity

The Periodic Table

Look at the Periodic Chart. The pattern arises due to a repetition or periodicity of chemical properties. The vertical columns of the charts are called groups, while the rows are referred to as periods.

Periodic Table of the Elements
 IA IIA IIIA IVA VA VIA VIIA VIIIA
   H  He
Li Be    B C N O F Ne
Na Mg IIIB IVB VB VI VIIB VIIIB IB IIB  Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
 Rb Sr  Y Zr Nb Mo Tc Ru Rh Pd  Ag  Cd  In Sn Sb Te I  Xe
 Cs  Ba Lu Hf Ta  W Re Os Ir  Pt Au  Hg Tl  Pb Bi Po At Rn

Note the numbering of the groups. The numbers from 1 - 18 are the internationally accepted numbers. We will also use the I - VIII "American" numbering system. Note that the "tallest" columns comprise what are referred to as the "representative elements" (IA - VIIIA).

Terms:

You should know the terminology above.

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© R A Paselk

Last modified 15 March 2013