- We assign quantum numbers by looking at the last electron of an atom.
- Principal Quantum Number (n) The shell
- Describes size and energy level of orbitals - corresponds to period (row) on the periodic table
- Refers to most outermost electron shell.
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- Means electrons have higher energy.
- Anything that falls within d-block:
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- n = period - 1
- Anything that falls within f-block:
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- n = period - 2
- Angular Momentum Quantum Number (l) The sub-shell
- Defines 3d shape of orbitals
- Any integer from 0 to n-1
- s-block s-orbitals
- l = 0
- p-block
- l = 1
- d-block
- l = 2
- f-block
- l = 3
Orbitals
- Lobes
- Where electrons can be found
- Nodes
- Electrons can never be found
- More nodes = higher energy (negative space)
- Total nodes = n - 1
- Angular Nodes
- Planes separating phases/lobes
- Radial Nodes
- Spherical nodes between shells
Magnetic Quantum Number
M_l
- Magnetic Quantum Number (M_l) Orbitals
- Defines spatial orientation
- Total number of possible orbitals in subshell = 2l + 1 = num possible M_l
Ml can have values from -l to +l.
When l = 1, ml can be -1, 0, or +1
Spin Quantum Number (Ms)
- Spin Quantum Number (Ms) Electron Spin
- Tells us the spin of last electron.
- Either ip or down
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- Up = +1/2
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- Down = -1/2
- Each orbital (value of Ml) can have two electrons and they cannot have the same spin.
Electron Configuration
- n + 1 + subscript of number of atoms in that group.
- Aufbau Principle
- Lower energy orbitals fill up first.
- Orbitals with same energy level are called degenerate.
- Ne Electron Configuration
- $$12^22s^22p^6$$
- O Electron Configuration
- $$12^22s^22p^4$$
- Mg Electron Configuration
- $$12^22s^22p^63s^2$$
- Ti Electron Configuration
- $$12^22s^22p^63s^23p^64s^23d^2$$
Noble Gas Configuration
- Allows us to start at the last noble gas
- Ti Electron Configuration
- $$[Ar]4s^23d^2$$
Valence Electrons
- Outermost Electrons
- Also known as valence electrons
- What participates in binding
- Number of valence = find highest n-value of s & p orbitals ... find largest n value and add all superscripts in s and p orbitals for that n-value.
- Octet
- When an atom has 8 valence electrons.
- Mg Electron Configuration
- $$12^22s^22p^63s^2$$
- Has two valence electrons
- Ionic Radius
- As we add more electron shells - the atomic radius increases
- As we add more protons - the atomic radius decreases
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- As we move DOWN and the the LEFT, the atomic radius INCREASES.
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- Atomic radius decreases as you move to the right.