Electron Arrangement in Atoms. Electron configurations Aufbau principle Pauli exclusion principle...
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Transcript of Electron Arrangement in Atoms. Electron configurations Aufbau principle Pauli exclusion principle...
ChemistryElectron
Arrangement in Atoms
Section 2 Terms Electron configurations Aufbau principle Pauli exclusion principle Hund’s rule
Go (con)Figure ELECTRON CONFIGURATIONS: Series
of sublevel notations which describes what sublevels electrons currently reside in
Tells you where the electrons are 3 Rules to electron configuration
• Aufbau’s Principle• Pauli Exclusion Principle• Hund’s Rule
Aufbau’s Principle Electrons
occupy orbitals of lowest energy first
Each box represents an orbital
Aufbau Diagram
Range of an energy level can overlap those of another
Think crossing your fingers
The Pauli Exclusion Principle
No more than two electrons in an orbital and they must have opposite spin• Spin can be thought of as
clockwise and counterclockwise
• Vertical arrows up or down indicate direction of spin
Hund’s Rule Must be one e- in
each orbital of equal energy before pairing
Remaining spot filled with e- of opposite spin
Writing Electron Configs
To write electron configs for an element:• Determine # of electrons the element has
The atomic number tells you how many e- if the element is neutral, which we will assume is the case
• Fill sublevels of lowest energy first Use Aufbau diagram (left side) to figure out who is
lowest Put electrons in orbital until filled
• For every electron in a sublevel, indicate with the sublevel name and a superscript Example: He = 2 e-, written as 1s2
C = 6 e-, written as 1s2 2s2 2p2
To figure out which sublevels filled first:• 1s• 2s 2p• 3s 3p 3d• 4s 4p 4d 4f• 5s 5p 5d 5f• 6s 6p 6d 6f
Section 2 Assignment Write the electron configurations for the
following elements B Cl P Ar Ca Ti Fe Hg Er
Aufbau Diagram
Aufbau Diagrams
Aufbau Diagrams