Noble-ity

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Page 175
Entry Task
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What 3 particles make up an atom? Protons, neutrons, electrons
What particles are in the nucleus? Protons & neutrons
What is the charge on a proton? positive
What is the charge on an electron? negative
What is the charge on a neutron? Neutral (no charge)
An element is determined by the number of what? protons
What happens in an ionic bond? One atom transfers electrons to
another atom
 What happens in a covalent bond? Atoms share electrons equally
 What happens in a polar covalent bond? Atoms share electrons
unequally
 What do you get when you change the number of electrons on an
atom? An ion
Entry Task
 Which scientist discovered the electron? Thomson
 Which scientist proposed a model of an atom that contained a nucleus?
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Rutherford
Which scientist proposed the “plum pudding” model of an atom?
Thomson
Most of the volume of an atom is made up of what? Empty space
Most of the mass of an atom is located where? nucleus
When looking at white light through a spectroscope (clear lightbulb,
sunlight), what did the spectrum look like? A rainbow
The electrons in the outermost energy shell of an atom are called?
Valence electrons
You cut a piece of gold in half repeatedly until you end up with the
smallest piece that can still be considered gold. What do you have? An
atom
What determines bond type? Difference in electronegativities
What is the energy required to take an electron from an atom? Ionization
energy
Noble-ity
Start a new thread/topic
Learning Target: What do spectral
lines tell me about the structure of
an atom?
Update TOC
Noble-ity
Read Intro p. 175-176
Read Process & Procedure Intro p.
176
Noble-ity P&P#1
Draw the Hydrogen Line Spectrum
in your notebook.
Label: longest wavelength, shortest
wavelength, highest energy, lowest
energy
Shortest wavelength
Highest energy
Longest wavelength
Lowest energy
Noble-ity P&P#2
 2a: How do you know that the Rutherford
model of atom structure did not explain
line spectra?
 The Rutherford model of the atom just
showed that electrons were outside of the
nucleus, but did not specify that they had
to be in specific locations around the
nucleus.
Noble-ity P&P#2
 2b: How do you know that each line is
associated with a different amount of
energy?
 Each line has a different color. Color
depends on wavelength, and color is a
form of light. Light is a form of energy.
Therefore, each color corresponds to a
different amount of energy.
Noble-ity P&P#2
 2c: What makes you think rapidly moving
electrons, not rapidly moving protons, are
responsible for spectral lines?
 Protons are about 1800 times heavier than
electrons. If light emissions requires a particle
to move rapidly between energy states, it
would seem more likely that electrons, which
are much lighter, would be better able to
move quickly.
Noble-ity P&P#2
 2d: How were differences in the amount of
dark space between lines of color important?
 Different sized dark spaces separate lines of
different color. The different colors are
associated with different amounts of energy.
The difference in size of dard spaces results
from electrons moving between energy levels
separated by different amounts of energy.
Noble-ity P&P#4
Read and take notes on Niels Bohr
p. 177-178
Niels Bohr
Bohr was a Danish physicist
Worked with Rutherford to
improve the model of the atom
Wanted to explain what was wrong
with Rutherford’s model
Niels Bohr
Most scientists believe that
electrons could orbit anywhere
around the nucleus.
Bohr believed that electrons could
only move in specific orbits.
How did he prove it?
Niels Bohr
He used spectral line data from
Hydrogen to prove his point.
Spectral lines are unique for each
element.
The lines only appear at specific
wavelengths.
Niels Bohr
Bohr predicted that electrons can
only absorb a specific amount of
energy.
He called this a quantum of
energy.
A quantum of energy is the specific
amount of energy needed for an
electron to move to a higher energy
shell.
Niels Bohr
When the electron returns to the
lower energy level, the quantum of
energy is released as a photon of
light  a spectral line seen through
a spectroscope
Each spectral line corresponds to a
quantum of energy.
Niels Bohr
 When the electron
returns to the lower
energy level, the
quantum of energy
is released as a
photon of light  a
spectral line seen
through a
spectroscope
 Each spectral line
corresponds to a
quantum of energy.
Niels Bohr
 The reason every element has a
different line spectrum is because
each element has a different number
and arrangement of electrons that can
absorb and release different quanta of
energy.
 Each element has a different number
of protons attracting the electrons,
which means that the energy levels are
located at different distances from the
nucleus.
Niels Bohr
Bohr proposed that electrons only
travel is specific paths – called
orbits.
An electron has a specific amount
of energy to keep it in its orbit.
It is not losing or gaining energy as
long as it stays in its orbit.
Niels Bohr
 To move to a higher orbit, an electron
must absorb an exact quantum of
energy.
 When it jumps back to its lower
energy level, it releases an exact
quantum of energy (photon of light)
 Bohr’s model and calculations worked
really well for Hydrogen, but were not
as accurate for bigger elements.
P&P #6a
 Sr2+ground state + energy  Sr2+excited state
 Sr2+excited state  Sr2+ground state + photon
 Which expression represents an electron
of a strontium ion absorbing energy? The
first equation because it shows the
electron absorbing energy and moving to
a higher energy level (excited state)
P&P #6b
Sr2+ground state + energy  Sr2+excited state
Sr2+excited state  Sr2+ground state + photon
Which expression represents an
electron of a strontium ion emitting
energy? The second one because the
energy is being emitted in a photon of
light.
P&P #6c
 Sr2+ground state + energy  Sr2+excited state
 Sr2+excited state  Sr2+ground state + photon
 What particle transports energy away
from the excited state of a strontium ion
when it falls to the ground state? A
photon carries the energy. The photon is
associated with a unique color of light.
P&P #6d
 Based on flame tests,
what is a reasonable
hypothesis about the
color of an emitted
photon from
strontium? Red, since
the flame test showed
a red color.
P&P #6d
 Sr2+ground state + energy  Sr2+excited state
 Sr2+excited state  Sr2+ground state + photon
 Did the heat of the flame ionize the
strontium ion? It was already ionized as
a result of dissolving in water. The
electrons are moving back and forth
between energy levels, they are not being
removed from the nucleus (ionized)

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