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Wednesday, October 21st, 2015
Bohr Model of the Atom
Brainstorm in your notes: What did Bohr’s model of the atom look like?
To Review
What did Bohr’s model of the atom look like?
To Review: Bohr’s Model
Nucleus
Electron
Orbit
Energy Levels
Fixed energy related to the orbit Electrons cannot exist between orbits The higher the energy level, the
further it is away from the nucleus An atom with maximum number of
electrons in the outermost orbital energy level is stable (unreactive)
Bohr Model of an Atom
Further away from the nucleus means more energy.
There is no “in between” energy
Energy Levels
First
Second
Third
Fourth
Fifth
Incr
easi
ng e
nerg
y
}
Quantum Mechanical Model
Modern atomic theory describes the electronic structure of the atom as the probability of finding electrons within certain regions of space (orbitals).
Niels Bohr &Albert Einstein
The Electron Cloud
The electron cloud represents positions where there is a probability of finding an electron.
The higher the electron density, the higher the probability that an electron may be found in that region.
There are two ways to state the location of an electron…
Quantum numbers – we will cover next time…
Electron configurations – the addresses of every electron in an atom (read the periodic table like a book!)
Atomic Orbitals – the address
Principal Quantum Number (n) = the energy level of the electron called “atomic orbitals”
The maximum number of electrons in an energy level = 2n2
Each s-orbital can hold two electrons.The p-sublevel can hold 6 electrons: how
many orbitals are in the p-sublevel?The D sub-level has 5 d-orbitals: so how many
electrons can it hold?
Summary
s
p
d
f
# of shapes (orbitals)
Max # of electrons
1 2 1
3 6 2
5 10 3
7 14 4
Sublevel
Starts at energy level
The closer an electron is to a proton, the more stable the
atom!
The most stable location for an electron is as close to the nucleus as it can get… that is its ground state configuration.
Aufbau Principle: electrons fill starting with the lowest energy level first
Pauli Exclusion Principle: Maximum 2 electrons per “orbital,” and electrons pair with opposite spin
Hunds’ Rule: electrons occupy orbitals with identical energy one at a time and in parallel, before pairing up
Electron Configuration Rules
Orbital Modeling Activity