Quantum Mechanical Model of Atoms Flashcards
1
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Quantum Mechanical Model
A
- proposes that electrons do not travel in defined orbits but rather are localized in orbitals
- In the current quantum mechanical model it is impossible to pinpoint exactly where an electron is at any given moment in time
2
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Orbitals
A
- a region of space around the nucleus defined by the probability of finding an electron in that region of space
- region of space around the nucleus that electrons are localized and move rapidly within
3
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Heisenberg Uncertainty Principle
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- It is impossible to simultaneously determine, with perfect accuracy, the momentum and the position of an electron
4
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Quantum Numbers
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- n = Principal
- l = Azimuthal
- ml = Magnetic
- ms = Spin
5
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Energy State
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- position and energy of an electron described by its quantum numbers
6
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Principal Quantum Number
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- n (first quantum number)
- describes the average energy of a shell
- the larger the integer value of n, the higher the energy level and radius of the electron’s shell
- energy difference between 2 shells = [1/n2i - 1/n2f]
- tells you the number of subshells (l)
7
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Azimuthal (angular momentum) quantum number
A
- l (second quantum number)
- refers to the shape and number of subshells within a given principal energy level (shell)
- n limits the value of l
- s, p, d, f
- range of possible values for l is: 0 to (n-1)
- s → l = 0 subshell
- p → l = 1 subshell
- d → l = 2 subshell
- f → l = 3 subshell
- (ie: electron in shell n = 4 and subshell l = 2 is said to be in the 4d subshell
- energies of the subshell increase with increasing l value (to the right and down)
8
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Formula for maximum number of electrons within a subshell
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4l + 2
9
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Magnetic Quantum Number
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- ml (third quantum number)
- specifies the orbital within a subshell where an electron is likely to be found
- Each orbital can hold a maximum of 2 electrons
- values are integers between -l and +l including 0
- ie: s subshell where l = 0 , ml = 0 → 1 orbital
- p subshell where l = 1, ml = -1, 0, +1
- d subshell where l = 2, ml = -2, -1, 0, +1, +2
- f subshell where l = 3, ml = -3, -2, -1, 0, +1, +2, +3
10
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Atomic Orbital Shapes
A
- The shape of orbitals, like the number of orbitals, is dependent on the subshell they are found in
- orbitals in the s subshell are spherical
- orbitals in the p subshell are dumbbell shaped alond x, y and z axes
11
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Spin Quantum Number
A
- ms (fourth quantum number)
- indicates the spin orientation of an electron (±½) of an electron in an orbital
- Whenever 2 electrons are in the same orbital they must have opposite spins
- often referred to as being paired
- electrons in different orbitals with the same ms are said to have parallel spins
12
Q
Subshell Energy Levels
A
- Electrons fill from lower to higher subshells according to the Aufbau principle aka building up principal
- Each subshell will fill completely before electrons begin to enter the next one
- you can recall the order the subshells are filled by the n+l rule or reading the periodic table
13
Q
n + l rule
A
- the lower sum of the values of the firs and second quantum numbers, n+l, the lower the energy of the subshell
- If two subshells posess the same n+l value, the subshell with the lower n value has a lower energy and will fill first
14
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electron configuration
A
- can be abbreviated by placing the noble gas that precedes the element of interest in brackets
- ie: an element in period 4 can be abreviated by starting with [Ar]
- uses spectroscopic notation (combining n and l values as a number and letter, respectively) to designate the location of electrons
15
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electron configuration of ion
A
- Anion: add electron to the end subshell until full
- Cation: take away electron from subshell with highest n, then highest l value