Chapter 5 Electrons in Atoms
Year
400BC
1808
1897
1916
1919
Event
____________________ proposes idea of atom
_________________ develops Atomic Theory
____________ uses cathode ray to discover electron
__________________ measures the mass of an e______________________ uses gold foil experiment to
discover nucleus
In 1897 J. J. Thomson discovered the electron
Atoms were known to be ___________________ neutral which meant
that there had to be some _____________________ charged matter to
balance the negative charges
BUT, Rutherford’s atomic model could not explain the
_______________________ properties of elements
In 1913, Niels Bohr came up with a new _________________ (Bohr was
a student of Rutherford)
Ernest Rutherford’s experiment ______________________ the plum
pudding model of the atom and suggested that there was a
_______________________ charged nucleus because most of the alpha
particles went straight through the gold foil
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He noticed that light given out when atoms were heated always
had specific amounts of __________________, so Niels Bohr proposed a
model that electrons in an atom must be orbiting the nucleus and
can reside only in fixed _____________________ levels
Similar to Bohr’s model, Schrodinger
describes the energy of __________________ with
certain values but does not involve an exact
_____________________ the electron takes around
the nucleus
This is similar to steps of a
__________________ (can climb up the
ladder, but cannot step in between the
steps)
The Quantum Mechanics View of the Atom (Schrodinger)
The quantum mechanical model does not describe the exact
________________ an electron takes around the nucleus, but
determines the _________________________ of finding an electron in a
Quantum is the amount of __________________ required to move an
certain area
electron from one energy level to another
In this model, electrons move similar to a rotating
The further away from the ___________________, the more energy the
_____________________ blade
electron has
You cannot tell its precise ___________________ at any instant because
it’s a blurry region, but you have information regarding the
_____________________ of finding an electron within a certain volume of
space
While Rutherford’s model described the __________________ the
electron moves, Erwin Schrodinger solved
____________________________ equations to describe the behavior of
Similar to a fuzzy cloud…the probability of finding an electron is
__________________ where the cloud is more dense
electron
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An Atomic Orbital is a region of space where
there is a high __________________________ of
finding an electron
Each energy sublevel corresponds to an
orbital of different ________________ describing
where the electron is likely to be found
(there are 4 different types of shapes)
Sublevel
# of Orbitals
Available
# of Electrons
Available
Chapter 5.2 – Electron Arrangement in Atoms
Each electron in an atom is assigned a set of four _________________
numbers. These help to determine the highest ______________________
of finding the electrons.
Filling order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Examples:
Three of these numbers (n, l, m) give the __________________ of the
electron
The fourth (s) describes the ____________________ of an electron in an
orbital.
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Electron Configurations can be written in terms of _______________
gases
To save space, configurations can be written in terms of noble
gases
Orbital Diagrams
3. Use arrows to represent the electrons in each orbital.
Rule #1 - Aufbau Principle
Electrons must ________________ the orbital with the lowest energy
first
Example: Oxygen
Used to show how ________________ are distributed within sublevels
Each orbital is ___________________ by a box and each electron is
represented by an arrow
Rule #2 - Pauli Exclusion Principle
Orbitals can only have _________ electrons max
The 2 electrons must have opposite spins
Notice that each box is drawn ____________________ than the last set
because it has more energy
Example: Oxygen
Rule #3 - Hund’s Rule
Example
Orbitals of equal _________________ are each occupied by one electron
before any pairing occurs
Example: Oxygen
Orbital Diagrams
1.Write the electron configuration
Section 5.3 – Atomic Spectra
When atoms ______________ energy, electrons move into
2. Construct an orbital filling diagram using boxes for each orbital
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________________ energy levels (excited state)
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When these _______________ return to their lower energy levels, they
lose _________________ by emitting light
Atomic Emission Spectrum – the discrete _________________
representing the __________________ of light emitted by an element
Calculating Wavelength of Light
c = speed of light (3 x 108 m/s2)
 = wavelength (called lambda)
 = frequency (called nu)
Atomic Spectra
Each ___________________ line in an emission _________________________
corresponds to one exact ______________________ of light emitted by
the atom
Ground State – lowest _______________ energy of the
____________________ in the Bohr model
The _________________ emitted by an electron moving from higher to a
lower __________________ level has a frequency directly proportional
to the energy __________________ of the electron
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