# Quantum Numbers Electron Configuration by kqm58610

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```									Quantum Numbers & Electron
Configuration
Heisenberg uncertainty
principle:
• States that it is impossible to determine
both the position and velocity of an
electron.
Quantum Theory
• Schrodinger hypothesized that electrons
have a dual wave-particle nature.
• Quantum theory describes wave
properties of electrons – if an electron
behaved ONLY like a particle, it would be
much easier to determine its location and
path.
– An orbital is the area where an electron is
probably located!
Quantum Numbers
• Quantum numbers are used to specify the
properties of atomic orbitals and the
properties of electrons in orbitals
– There are 4 quantum numbers!
Quantum Numbers
1. PRINCIPAL Quantum Number – n
*describes the principal (main) energy
levels of electrons in an atom
* increase in n = increase in energy
* maximum number of electrons in an
energy level
Quantum Numbers
Angular Quantum Number – l
* determines the shape of the orbital
* the number of sublevels is equal to the principal quantum number
* four shapes of the energy sub levels are:
»   s = spherical (groups 1&2)
»   p = dumbbell (groups 13-18)
»   d = double dumbbell (groups 3-12)
»   f = too complex to describe (groups 4-5)

* Each of the sublevels (s, p, d, f) contain orbitals
* Each orbital can hold 2 electrons
»   s = 1 orbital      = 2 e-
»   p = 3 orbitals     = 6 e-
»   d = 5 orbitals     = 10 e-
»   f = 7 orbitals     = 14 e-
Quantum Numbers
MAGNETIC Quantum
Number - m
* describes the
orientation (direction)
of the orbital in space
(x, y or z axis)
* the number of
orbitals = the number
of different
orientations
Quantum Numbers
SPIN Quantum Number
* describes the direction of the electron
spin
* spins clockwise (+ ½) or
counterclockwise (– ½)
* two electrons in the same orbital MUST
HAVE OPPOSITE SPINS!!!
Three Rules for writing notations
(determining how energy levels are filled
in atoms)

Aufbau principle
* electrons enter orbitals of the lowest energy
first
Three Rules for writing notations -
determining how energy levels are filled
in atoms

Pauli exclusion principle
* this limits the number of electrons in each
orbital to 2: 1 spin up ↑, and 1 spin down ↓
Three Rules for writing notations -
determining how energy levels are filled
in atoms

Hund’s Rule
* when electrons occupy orbitals of equal
energy, ONE electron enters each orbital
until ALL are ½ filled with electrons
spinning in the same direction (all up or all
down), then the orbitals are filled with the
spin electrons

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