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Bohr Model (Shell Model). Evidence suggested electrons occupied specific energy levels (shells) while “orbiting” around nucleus Essentially based on Coulomb’s Law. k = coulomb’s constant q = object with a charge r = radius (distance between the 2 charged particles). - PowerPoint PPT Presentation
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Bohr Model (Shell Model)• Evidence suggested electrons occupied specific
energy levels (shells) while “orbiting” around nucleus
• Essentially based on Coulomb’s Law
𝑭𝒐𝒓𝒄𝒆=𝒌 𝒒𝟏𝒒𝟐
𝒓𝟐
k = coulomb’s constantq = object with a charger = radius (distance between the 2 charged particles)
Was used to help explain why electrons didn’t come “crashing” into the nucleus (since opposites attract)• Attractive force
between nucleus and electron is balanced by electron’s centrifugal force
The Bohr model makes great predictions BUT there’s a couple things about electrons we discovered:• Uncertainty • Electron spin
Uncertainty:- Heisenberg Uncertainty Principle
We can never know BOTH the:• Location of an electron• Momentum of an electron
Because of this, we realized that electrons live in these “clouds” of probability• Don’t follow specific orbits
Orbital• Where electrons
spend their time
Electrons have a Spin• Clockwise or counter-clockwise
magnetic spin
As a result of this electron spin:• Only two (max) electrons can
exist in an orbital
This forced us to modify our “shell” (Bohr) model in order to better align with the evidence of reality• Quantum mechanical model of the atom• Computers allowed us to complete complex equations and software to predict how
atoms are going to interact
Orbitalss orbital
p orbitals
d orbitals
f orbitals
ALL of these orbitals simply represent “clouds” of probability where electrons sit
Quantum Numbers
Size (n)• Size of the orbital• As n gets larger then the area in which the electron occupies gets
larger as well
Shape (l)• Shape of the orbital• Can be either an s, p, d, f
Orientation (ml)• Tells us the number of orientations the orbitals can have• s 1 orientation• p 3 orientations• d 5 orientations• f 7 orientations
Spin (ms)• Clockwise (+1/2)• Counter-clockwise (-1/2)• Dictates that only 2 electrons can exist in an orbital
These numbers allow us to predict WHERE electrons are most likely to be found which allows us to predict:• What an atom
looks like• How atoms
are going to interact
Electron Configuration
• Distribution of electrons• Where the electrons are found in atoms
OR in ions
Ionization energy• Amount of energy it takes
to remove an electron• Can be quantified using
Coulomb’s Law
Multielectron atoms or ions• Shells, subshells, and orbitals similar ionization energy
Nucleus Core electrons Valence electrons
shield
Atomic number
hydrogen
Each box represents and orbitalEach arrow represents an electron
Atomic number
helium
Each box represents and orbitalEach arrow represents an electron
Atomic number
lithium
Each box represents and orbitalEach arrow represents an electron
Atomic number
beryllium
Each box represents and orbitalEach arrow represents an electron
Atomic number
boron
Each box represents and orbitalEach arrow represents an electron
Atomic number
carbon
Each box represents and orbitalEach arrow represents an electron
Atomic number
nitrogen
Each box represents and orbitalEach arrow represents an electron
Atomic number
oxygen
Each box represents and orbitalEach arrow represents an electron
Atomic number
fluorine
Each box represents and orbitalEach arrow represents an electron
Atomic number
neon
Each box represents and orbitalEach arrow represents an electron
Atomic number
sodium
Each box represents and orbitalEach arrow represents an electron
Atomic number
magnesium
Each box represents and orbitalEach arrow represents an electron
Periodicity1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d
7s 7p
hydrogen 1s1
Periodicity1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d
7s 7p
boron 1s22s22p1
Periodicity1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d
7s 7p
neon 1s22s22p6
Periodicity1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d
7s 7p
sodium 1s22s22p63s1
Periodicity1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d
7s 7p
chromium 1s22s22p63s23p64s23d4
[Ar]4s23d4Same thing