# Quantum Numbers n, l, m, and s Used 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? Energy Level n

1 2 s = 1 orbital x 2 e-/orbital = 2 ep = 3 orbitals x 2 e-/orbital = 6 ed = 5 orbitals x 2 e-/orbital = 10 ef = 7 orbitals x 2 e-/orbital = 14 eE sublevel Type of orbital # of orbitals s s p 1 1 3 # e- in orbital

# e- = 2n2 2 2(12) = 2 2 6 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=PLD1C287B0E1484083&index=1&featur e=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 1 s Episode 304 Nitrogen 1s2 2s2 2p3 1 s 2

s 2p Hunds 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