Rules for building an atom
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Pauli Exclusion Principle: No two e- can have the same 4 quantum numbers
Aufbau Principle: e- go into the lowest available orbital
Hund’s Rule: e- try to stay unpaired if possible
Note on magnetism: If an atom has unpaired e-, it has a weak, but measurable,
magnet field paramagnetic. only paired electrons  diamagnetic.
To determine electron configuration
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f 5g
6s 6p 6d 6f 6g…
7s 7p 7d 7f 7g…
Homework
Pg 191 #1, Pg 194#6,7,8,10,11
Pg 197 #2, 4, 11
Read Pg 196 – Anomalous Electron Configurations
Lab Exercise Quantitative Paramagnetism Pg 215
Prereading Pg 224-230, Pg 251-253
Building an atom Part 2
Determine electron configuration
Determine the electron configuration of:
a) Manganese
b) Yttrium
c) Iodide ion
d) Zinc ion
Short Form Electron Configuration
 Find the element on the periodic table.
 Look for the inert gas just previous to it. Use this as the core of you
configuration. (i.e. [Xe])
 Continue the pattern from there. Use what you know about the periodic table
to help you.
Short form configuration for silver.
Special Electron Configurations
Some elements, such as silver, have electron configuration different from what we
would expect.
Predicted:
Actual:
This is due to the fact that completely filled subshells, empty subshells, and half
filled subshells are lower in energy.
Orbital Diagrams
 A visual way of showing electron configuration.
 Figure out electron configuration
 Represent each orbital with a circle or a square.
 Put electrons in using lines or arrows
For example:Strontium
Homework
Short form electron configuration for:
a) zirconium b) arsenic c) iron 2+,3+ and 6+
Orbital diagram: a)bromine
b) chromium
Pg 197#6,7,9, 13