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Section 5.3 Quantum numbers and Atomic Orbitals Quantum numbers are numbers that specify the properties of atomic orbitals and of the electrons in that orbital It’s the electrons “address”

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Four Quantum Numbers Principal quantum number Orbital quantum number Magnetic quantum number Spin quantum number

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Principal quantum number Symbol, n Indicates the main energy levels To this point, only 1-7 Where do we see 7 main energy levels in this room?

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Orbital quantum number Shape of an orbital Four shapes s, p, d, and f Within each main energy level there are different shapes of orbitals

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Shapes of orbitals s orbitalp orbitals

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Shapes of d orbitals

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Examples of f-shaped orbitals

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Magnetic quantum number Indicates the orientation (or position) of an orbital around the nucleus –s orbital has 1 orientation –p orbitals have 3 orientations –d orbitals have 5 orientations –f orbitals have 7 orientations Each orbital can contain only 0, 1, or 2 electrons.

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Spin quantum number Indicates the spin of the electron –+1/2 –-1/2 –So if there are two electrons in one orbital, they spin in opposite directions *** no two electrons can have the same 4 quantum numbers***

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Electron configurations (electron arrangements) Pauli Exclusion Principle –No two electrons in the same atom will have the same set of 4 quantum numbers

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How to “read” orbitals How we determine which orbital gets filled with electrons first? Must follow the ________________: –Orbital of Lowest energy gets filled before going to the next lowest energy orbital –In other words we fill from lowest energy to highest energy –“building up” principle: electrons occupy the lowest-energy orbital that is available. –For example, Hydrogen’s electron goes into the __ orbital, because it is the lowest energy orbital

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Electron configurations (electron arrangements) How do we know which orbitals are higher or lower in energy? –Read Periodic Table from Left to Right, Top to Bottom

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Periodic Table Sections

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3 types of notation Orbital Notation Electron-Configuration Notation Electron Dot Notation

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Orbital Notation Unoccupied orbital __ Orbital with1 e-↑ or ↓ Orbital with 2 e-↓↑ Example: HydrogenExample: Lithium Example: HeliumExample: Oxygen

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Electron configurations (electron arrangements) Hund’s rule –Orbitals of equal energy are each occupied by 1 electron before a 2 nd electron is added. –All electrons in singly occupied orbitals must have the same spin –For example, there are 3 p orbitals. If you have 3 electrons, there will be one in each orbital and all will have spin quantum number of +1/2 or -1/2 –Example N:

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Electron-Configuration notation Similar to orbital notation, but uses superscripts instead of lines Example: Hydrogen Example: Helium Example: Lithium

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Electron-Dot Notation Uses only the Valence electrons Valence electrons = the electrons in the highest (outermost) main energy level H He K

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Practice Problems (orbital and dot notation) Carbon Sodium Sulfur

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Shorthand Notation Use the last noble gas before your element as a “building block” Example: Phosphorous

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Practice Problems (d and f orbitals) Fe Au

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Trick to Electron Dot Notation Use the group number that the element is in Hydrogen is in group 1, 1 valence electron Oxygen is in group 6, 6 valence electrons These 8 groups are sometimes called the 8 “main groups”

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