Quantum Numbers
• n, l, m, and s
– Used to describe an electron in an atom
• Probable location
• n
– Principal Quantum Number
– Represents main energy level of electron
• Maximum # of electrons in an energy level = 2n2
• Example: What is the maximum number of
electrons that can be in the 5th main
energy level?
– 2(52)
– Electrons in 7th energy level?
Episode 304
Quantum Numbers
• l
• The 2nd quantum number
– Angular momentum quantum number
• Describes the orbital shape within an
energy level
• Number of orbital shapes possible in an
energy level = n
http://www.youtube.com/watch?v=KjNgq16jEY&list=PLD1C287B0E1484083&index=9&feature=plcp
Episode 304
Orbital Shapes
•
•
•
•
•
Designated s, p, d, and f
Level 1: s
Level 2: s, p
Level 3: s, p, d
Level 4: s, p, d, f
Episode 304
How many electrons can each
sublevel hold?
•
•
•
•
s = 1 orbital x 2 e-/orbital =
p = 3 orbitals x 2 e-/orbital =
d = 5 orbitals x 2 e-/orbital =
f = 7 orbitals x 2 e-/orbital =
Energy Level
E sublevel
n
Type of orbital
1
2
2 e6 e10 e14 e-
# of orbitals
# e- in orbital
# e- = 2n2
s
s
1
1
2
2(12) = 2
p
3
6
2
2(22) = 8
Episode 304
Quantum Numbers
• m
• The 3rd quantum number
– Magnetic Quantum Number
• Describes the orientation of the orbital
in space
Episode 304
Quantum Numbers
• s
• The 4th quantum number
– Spin Quantum Number
http://www.youtube.com/watch?v=2ypC7rnFXLU&list=PLD1C287B0
E1484083&index=1&feature=plcp
• Describes the spin of the electron in orbital
• Ground state
• Lowest energy arrangement of electrons
– Aufbau Principle
Episode 304
Diagonal Rule
Examples:
• Hydrogen
– 1 electron
– 1s1
• Lithium
– 3 electrons
– 1s2 2s1
• Nitrogen
– 7 electrons
– 1s2 2s2 2p3
Episode 304
• Electron Configurations
– Describes the electron distribution within
an atom
• Longhand electron configuration
– Nitrogen 1s2 2s2 2p3
• Orbital Notation
– Uses arrows to represent electrons
• Examples:
– Hydrogen 1s1
1s
Episode 304
Nitrogen
• 1s2 2s2 2p3
1s
2s
2p
• Hund’s Rule
• Orbitals of equal energy are each occupied by one
electron before any orbital is occupied by a second
electron (spinning in opposite direction)
• Pauli Exclusion Principle
• No two electrons in the same atom can have the
same set of 4 quantum numbers
Episode 304