CHEMISTRY
November 5, 2014
Electron Spectrum
SCIENCE STARTER
• You have 5 minutes. You
are seated and quiet
• Do the Science Starter
• The Science Starter will be
graded during class.
Question 1
• The electron cloud is divided into regions
called principal energy levels/shells. Based on
the picture above, circle the best answer for
the following prompt: What is the lowest
energy level?
a.
b.
c.
d.
I Energy Level
II Energy Level
III Energy Level
IV Energy Level
Question 2
• The first energy level can hold up to 2
electrons. How many electrons can the 3rd
energy level hold?
Question 3
• The distribution of the electrons among the
shells (energy levels) is called the electron
configuration. The electron configuration can
be found on the periodic table.
a. For an element, where on the period table is the
electron configuration located?
b. What is the electron configuration for the
element carbon (C)?
Question 4
• The electron configuration provides the
following information: the number of shells
(energy levels) and the number of electrons in
each shell.
a. How many shells does the element carbon have?
b. How many electrons is in the first shell?
c. How many electrons is in the 2nd shell?
OBJECTIVES
• When an electron in an atom gains a
specific amount of energy, the electron
is at a higher energy state (excited
state). (3.1j)
• When an electron returns from a higher
energy state to a lower energy state, a
specific amount of energy is emitted.
This emitted energy can be used to
identify an element. (3.1k)
AIM
• What makes the colors
seen in fireworks?
EVIDENCE BASED TEMPLATE
• ON YOUR EVIDENCE BASED TEMPLATE, WRITE
DOWN THE AIM AS THE GUIDED QUESTION
• What makes the colors seen in fireworks?
• During the video, you will need to come up
with the following 2 things:
– Claim
– 2 evidence to support the claim
CLAIM
• Claim sentence starter:
• The color as seen in fireworks is
caused by
___________________
FIREWORK COLOR
• The color as seen in fireworks is
caused by HEATING a mixture of
metal salts and metal oxides which
react to produce an array of colors.
COMMON METAL SALTS
• Metal salts that are commonly used in
firework displays include: strontium carbonate
(red fireworks), calcium chloride (orange
fireworks), sodium nitrate (yellow fireworks),
barium chloride (green fireworks) and copper
chloride (blue fireworks). Purple fireworks are
typically produced by use of a mixture of
strontium (red) and copper (blue) compounds.
SODIUM
• Two TYPES OF PHOTONS!
• Both are yellow with different wavelengths
•
Sodium Emission Lines
400
500
600
Wavelength in nanometers
700
COPPER
– Eight different types of
photons.
– A purple one, a blue one,
and several wavelengths
of greens and yellows.
BRIGHTLINE SPECTRUM
• The individual
photon colors
emitted by the
electrons in
any atom form
the “atomic
emission
spectrum”
• Also called
“brightline
spectrum”
ORDER OF COLORS
• red, orange, yellow, green, blue, indigo, violet
• Red has the longest wavelength and the
lowest energy.
• Violet has the shortest wavelength and the
highest energy.
SCIENCE BEHIND
• Heating up metal salts and metal oxides which
react to produce an array of colors.
• Atoms absorb the energy causing its electrons
to move from from their lowest energy state
to a higher excited state.
• As the electrons fall down to a lower energy
state, the excess energy gets emitted as light.
• Each element releases a different amount of
energy and this energy is what determines the
color or wavelength of the light that is
emitted.
BRIGHT LINE SPECTRUM
• Compounds and metallic ions produce
characteristic colors when placed in a flame.
When these “flame tests” are passed through
a prism, a bright line spectrum (black
background with colored slits) can be seen.
BRIGHT LINE SPECTRUM (CONT’)
• A spectrum is produced when radiation from
light sources is separated into different
wavelength components.
• The bright line spectrum contains radiation of
only specific wavelengths of light.
ATOMIC SPECTRA
• Continuous Spectrum – If white light is passed
through a prism, a continuous spectrum
(rainbow) can be observed.
SPECTRAL LINES
• Spectral lines are the fingerprints of the
elements!
GROUND STATE VS EXCITED STATE
• The lowest energy state of an electron is
called “ground state.”
• When an electron is in a higher energy state, it
is called “excited state.”
GROUND STATE
• An electron in its lowest possible energy level
• Each electron energy level contains the
maximum number of electrons that it can
hold.
EXCITED STATE
• An electron that has gained energy and moved
to a higher energy level – it’s very unstable!
• Example: 12Mg
– Ground State:
• 2–8–2
– Excited state e- configuration:
• 1–8–3
• 2–7–3
• 2–6–4
PHOTONS
• If a photon of light strikes an atom, the energy in
the light may be transferred to the lower energy
electrons (the energy is absorbed by the electron)
• This puts the electrons into an excited state
causing the electron to moves to a higher energy
level.
• This is an unstable situation.
• The excited electron loses the extra energy (emits
energy) and fall back to the lower energy level.
BRIGHTLINE SPECTRUM
When only certain photons are observed, it
means that only light packets of a particular
type are being emitted!
• Each photon has a specific energy value.
• So only certain energy exchanges are
happening within the heated substance.
• So there must only be certain ways of
changing the energy in the substance!
EMISSION
• Atoms have “layers” of electrons called energy
levels.
• Each energy level has electrons with a certain
amount of energy in them that matches the level.
• When the electrons change levels, they have to
gain or lose energy to do so.
• Each time they lose energy, they emit a bundle of
energy.
• We see that bundle as a photon!
QUANTUM
• A specific quantity of light
• Bohr said that when energy is added to atoms,
the electrons gain a “quantum” of energy to
move to a higher level.
• When electrons relax back to their normal
state, they emit a quantum of energy to go
back to the lowest level.
PHOTON
• Photon is just the name for a quantum of light
• Electron Transition – when an electron moves from
one level to another
– When an electron transitions to a higher energy level, a
photon is absorbed.
– When an electron transitions to a lower energy level, a
photon is emitted.
PHOTON
• The emitted photon is just a “piece” of light.
• It has a specific energy value, so it has a
specific wavelength, frequency and color
• If you can measure the wavelength of the
photon, you can calculate its energy.
CONCLUSION
• Atom of each elements emits
unique photons of specific
energies