PhyChem 3 Midterm Exam Flashcards
In a vacuum, electromagnetic travels in a _____ in waves.
Speed of light
Name the 3 properties of a wave.
- Frequency
- Wavelength
- Amplitude
It is the height of a wave
Amplitude
Any region of the ________ includes a range of wavelengths.
electromagnetic spectrum
the light emitted by hot objects
black body radiation
the flow of current when light strikes a metal
the photoelectric effect
the specific colors emitted from a substance that is excited. —can only be explained if energy consists of “packets” (quanta) that occur in, and thus change by, fixed amounts. The energy of a quantum is related to its frequency.
atomic spectra
According to the _________, an atomic spectrum consists of separate lines because an atom has certain energy levels (states) that correspond to electrons in orbits around the nucleus
Bohr model
The _________ of the atom changes when the electron
moves from one orbit to another as the atom absorbs (or emits) light of a specific
frequency.
energy
_____________ means that matter has wave like properties and energy has particle like properties
Wave-particle duality
These properties are observable only on the atomic scale, and because of them, we
can never simultaneously know the position and speed of an electron in an atom
wave properties of matter and particle properties of energy
According to the _____________, each energy level of the atom is associated with an atomic orbital a mathematical description of the electron’s position in three dimensions
quantum-mechanical model of the H atom
We can know the
_____________ that the electron is within a particular tiny volume of space, but not its
exact location.
probability
The probability is _________ for the electron being near the nucleus, and it _________ with distance.
highest, decreases
Quantum numbers denote each atomic orbital’s energy. An energy level consists of sublevels, which consist of orbitals
Quantum numbers n is _________
principal quantum number
Quantum numbers l is __________.
angular momentum quantum number / azimuthal quantum numbers
Quantum numbers m(l) is _____________.
Magnetic quantum number
Quantum numbers m(s) is _____________.
Electron spin quantum number
Thus, for the H atom only, the energy levels depend solely on the _________________.
principal quantum number (n)
In the H atom, there is only one type of ______________: the attraction between nucleus and electron
electrostatic interaction
______________________had established the idea of individual units of matter.
Dalton’s atomic theory
________________substituted nuclear atoms for “billiard balls” or “plum puddings.”
Rutherford’s model
In contrast, energy is __________ and its quantity can change continuously.
massless
Visible light, x-rays, and microwaves are some of the types of ________________.
electromagnetic radiation
also called electromagnetic energy or radiant energy
electromagnetic radiation
All electromagnetic radiation consists of energy propagated by ________________ that increase and decrease in intensity as they move through space.
electric and magnetic fields
The wave properties of electromagnetic radiation are described by three variables and one constant. NAME THE THE 3 VARIABLES AND 1 CONSTANT.
3 variables:
(1) frequency, (2) wavelength, (3) amplitude
1 constant:
(1) speed
______________is the product of its frequency and wavelength.
Speed
The unit for speed is _________.
m/s
________________is the distance between any point on
a wave and the corresponding point on the next crest (or trough) of the wave, that is,
the distance the wave travels during one cycle.
wavelength
________________of a wave is the number of cycles it under
goes per second, expressed by the unit 1/second [s-1; also called a hertz (Hz)].
Frequency
Since the product of wavelength and frequend is a __________, they have a _____________ relationship.
constant,
reciprocal
radiation with a _______ frequency has a _______ wavelength, and vice versa:
high,
short
_____________ of a wave is the height of the crest (or depth of the trough).
Amplitude
It is related to the intensity of the radiation, or its brightness in the case of visible light.
Amplitude
All waves in the spectrum travel at the same speed through a vacuum but ________________.
differ in frequency and, therefore, wavelength.
what color has a wavelength of < 750 nm.
red
what color has a wavelength of 400 nm.
violet
Light of a single wavelength
is called __________(Greek, “one color”).
monochromatic
light of many wavelengths is _____________.
polychromatic
The region adjacent to visible light on the short-wavelength end consists of ___________radiation.
ultraviolet (UV)
Name the 7 regions of radiation in the electromagnetic spectrum.
UV, visible, radio, gamma, microwave, x-ray, infrared.
Arrange in increasing frequency:
UV, visible, radio, gamma, microwave, x-ray, infrared.
radio< microwave< infrared< visible< UV< x-ray< gamma
Arrange in increasing wavelength:
UV, visible, radio, gamma, microwave, x-ray, infrared.
gamma< x-ray< UV< visible< infrared< microwave< radio
Which has a shorter wavelength and higher frequency?
Visible or Infrared
Visible
A dental hygienist uses x-rays ( 1.00 Å) to take a series of dental radiographs while the patient listens to a radio station (325 cm) and looks out the window at the blue sky (473 nm). What is the frequency of the electromagnetic radiation from
each source? (Assume that the radiation travels at the speed of light, 3.00x10^8 m/s.)
x-rays: 3.00x10^18 s^-1
radio station: 9.23x10^7 s^-1
blue sky: 6.34x10^14 s^-1
In our everyday world, matter and energy behave very __________.
differently
Light of a given wavelength travels at different
speeds through various ___________—vacuum, air, water, quartz, and so forth.
transparent media
Therefore, when a light wave passes from one medium into another, the __________ changes
speed of the wave
The speed of a light wave
passing between media changes immediately, which bends its path.
Refraction
A wave bends around both edges of a small opening, forming a semicircular wave.
Diffraction
When waves of light pass through two adjacent slits, the nearby emerging circular waves interact through the process of ________________.
interference
Three observations involving matter and light confounded physicists at the turn
of the 20th century:
blackbody radiation, the photoelectric effect, and atomic spectra.
________________interference happens when two waves overlap in such a way that they combine to create a larger wave
Constructive
_____________interference happens when two waves overlap in such a way that they cancel each other out
Destructive
It is when a solid object is heated to about 1000 K,
it begins to emit visible light.
blackbody radiation
characteristic of blackbody
radiation, light given off by a hot ___________.
blackbody
He proposed that a hot, glowing object could emit (or absorb) only certain quantities of energy
Max Planck (1900)
Formula for Planck’s equation
E=nhv
Planck’s constant
6.626x10^-34 J*s
A hot object’s radiation must be emitted by its __________.
atoms
If each atom can _______ only
certain quantities of energy, it follows that each atom has only certain quantities of energy. Thus, the energy of an atom is ______________.
emit,
quantized
it occurs in fixed quantities, rather than being continuous
quantum
Each change in an atom’s energy occurs when the
atom absorbs or emits one or more “packets,” or definite amounts, of energy. Each
energy packet is called a __________.
quantum
plural for quantum
quanta
A quantum of energy is equal to _______.
hv (planck’s constant multiplied to frequency
an atom changes its energy state by emitting (or absorbing) one or more ___________.
quanta
the energy of the emitted (or absorbed) radiation is equal to the ____________ in the atom’s energy states.
difference
When light shines on a metal, electrons can be ejected from the surface of the metal in a phenomenon known as the____________.
Photoelectric effect
The 2 features of the photoelectric effect:
(1) Presence of a threshold frequency
(2) Absence of a time lag.
Albert Einstein proposed in 1905 that light itself is particulate, quantized into tiny “bundles” of energy, later called _______________.
photons
A ____________ is an idealized object that absorbs all the radiation incident on it.
Blackbody
__________ depends on frequency.
Energy
A student uses a microwave oven to heat a meal. The wavelength of the radiation
is 1.20 cm. What is the energy of one photon of this microwave radiation?
E= 1.66x10^-23 J
According to ___________, an atom has only certain quantities of energy (E= nhv), and it can change its energy only by absorbing or emitting a photon whose energy equals the change in the atom’s energy.
quantum theory
_____________ involved the light emitted when an element is vaporized and then excited electrically
Atomic spectra
When light from electrically excited gaseous atoms passes through a slit and is refracted by a prism it creates a _____________.
line spectrum
a series of fine lines at specific frequencies separated by black spaces
line spectrum
Each spectrum is _________ of the element producing it.
characteristic
Using data, not theory, the Swedish physicist _________ (1854–1919) developed a relationship, called the Rydberg equation
Johannes Rydberg
it predicts the position and wavelength of any line in a given series.
Rydberg equation
Write Rydberg equation
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Electrically excited H atoms emit a beam of light that is narrowed by a _____ and dispersed by a _______ to create a line spectrum.
slit,
prism
________________, a young Danish physicist suggested a model for the H atom that did predict the existence of line spectra.
Niels Bohr (1885–1962)
In this model, Bohr used Planck’s and Einstein’s ideas
about quantized energy and proposed three postulates.
The Bohr Model
Answer either Postulate 1, 2, or 3:
The atom changes to another stationary state (the electron moves to another orbit)
only by absorbing or emitting a photon. The energy of the photon equals the difference
in the energies of the two states
Postulate 3
Answer either Postulate 1, 2, or 3:
Each state is associated with a fixed circular orbit of the electron around the nucleus.
The higher the energy level, the farther the orbit is from the nucleus.
Postulate 1
Answer either Postulate 1, 2, or 3:
The atom does not radiate energy while in one of its stationary states.
Postulate 2
__________ is a positive integer
(1, 2, 3, . . .) associated with the radius of an electron orbit, which is directly related
to the electron’s energy.
quantum number
The lowest energy level
ground state
The higher energy level
excited state
The most stable arrangement
ground state
Atoms enter the _________ when they absorb energy and an electron moves from a lower energy level to a higher energy level.
excited state
energy equals the difference
between lower and higher energy levels
Absorption
If an H atom in a higher energy level (electron in farther orbit) returns to a lower energy level (electron in closer orbit),
Emission
A __________ results when a photon of specific energy (and thus frequency) is emitted.
spectral line
an atomic spectrum is not continuous because the
atom’s energy is not continuous, but rather has only ______________.
certain states
Bohr’s model accounts for __________ series of spectral lines of hydrogen
three
When electrons drop from outer orbits to the n=______ orbit (second excited state), the emitted photons create the infrared series of lines.
3
The visible series arises when electrons drop to the
n=______ orbit.
2
the ultraviolet series arises when electrons drop to the n=_____ orbit (ground state).
1
___________ do not move in fixed, defined orbits
electrons
The bohr model’s central idea is that __________.
the energy of an atom occurs in
discrete levels, and an atom changes energy by absorbing or emitting a photon of
specific energy.
The _________ sign for the energy appears because we define the zero point of the atom’s energy when the electron is completely
removed from the nucleus. Thus, E= 0 when n is infinity, so E<0 for any smaller n.
negative
A hydrogen atom absorbs a photon of UV light and its electron enters the n=4 energy level. Calculate (a) the change in energy of the atom and (b) the
wavelength (in nm) of the photon.
(a) E=2.04x10^-18 J
(b) 97.4 nm
An _______________ is produced when atoms in an excited state emit photons characteristic of the element as they return to lower energy states.
emission spectrum
An _______________ is produced when atoms absorb photons of certain wavelengths
and become excited from lower to higher energy states.
absorption spectrum
A ____________ can also be used to measure the concentration of a substance in a solution
spectrometer
The ______________, the amount of light of a given wavelength absorbed by a substance, is proportional to the number of molecules.
absorbance
light emitted by electrically excited atoms of an element appears as separate __________.
spectral lines
____________ use an empirical formula (the Rydberg equation) to determine the
wavelength of a spectral line. Atomic hydrogen displays several series of lines.
Spectroscopists
To explain the existence of ___________, Bohr proposed that an electron moves in fixed orbits. It moves from one orbit to another when the atom absorbs or emits a photon whose energy equals the difference in energy levels (orbits).
line spectra
______________ is an instrumental technique that obtains emission and absorption spectra used to identify substances and measure their concentrations.
Spectrometry
Bohr’s model was a perfect case of fitting theory to data: he assumed that an atom
has _____________ in order to explain line spectra.
only certain energy levels
Attempting to explain why an atom has fixed energy levels, a French physics student, ______________, considered other systems that display only certain allowed motions, such as the vibrations of a plucked guitar string.
Louis de Broglie
De Broglie proposed that
if energy is particle-like, perhaps matter is ____________.
wavelike
He reasoned that if __________
have wavelike motion in orbits of fixed radii, they would have only certain allowable frequencies and energies.
electrons
Combining Einstein’s famous equation for mass-energy equivalence (E=mc^2)
with the equation for the energy of a photon (E= hn=hc/wavelength), de Broglie derived an equation for the wavelength of any particle of mass m—whether planet, baseball, or electron—moving at speed u. WRITE THE EQUATION
lambda=h/mu
According to this equation for the______________, matter behaves as though it moves in a wave.
de Broglie wavelength
An object’s wavelength is ____________ proportional to its mass.
inversely
Find the de Broglie wavelength of an electron with a speed of 1.00x10^6 m/s (electron mass=9.11x10^-31 kg; h=6.626x10^-34 kg*m^2/s).
h/mu= 7.27x10^-10 m
If electrons travel in waves, they should exhibit ____________ and ____________.
diffraction,
interference
A fast-moving electron has a wavelength of about ________so a beam of such electrons
should be diffracted by the spaces between atoms in a crystal—about 10^-10 m.
10^-10 m
In 1927, ___________ and _____________ guided a beam of x-rays and then a beam of
electrons at a nickel crystal and obtained two diffraction patterns
C. Davisson and L. Germer
Matter is ________ and massive, while energy is __________ and wavelike.
particulate,
continuous
_______________ is
diffracted by
metal crystal.
electron beam
Energy and Matter
particulate, massive, wavelike
QUANTUM THEORY
It states that it is impossible
to know simultaneously the position and momentum (mass times speed) of a particle.
Uncertainty principle
In 1927, the German physicist _____________ postulated the uncertainty principle
Werner Heisenberg
Electrons exhibit ___________, just as light waves do, and photons exhibit__________________, just as objects do. This wave-particle duality of matter and energy is observable only on the atomic scale.
diffraction,
transfer of momentum
In 1926, ____________ derived an equation that is the basis for the quantum-mechanical model of the H atom
Erwin Schrödinger
It examines the wave nature of objects on the atomic scale.
quantum mechanics
_______________, a mathematical description of the electron’s
matter-wave in three dimensions
atomic orbital
_____________________,
represents a set of mathematical operations that, when carried out with a particular
(psi), yields one of the allowed energy states of the atom. Thus, each solution of the
equation gives an energy state associated with a given atomic orbital.
Hamiltonian operator
the ground state of the H atom, the _________________ decreases with distance from the nucleus along a line
electron probability
density
Name the 3 probable locations of the electron.
(1) Probability of the electron being in some tiny volume of the atom.
(2) Total probability density at some distance from the nucleus. To find radial probability distribution.
(3) Probability contour and the size of the atom
visualize an atom with a _____% probability contour
90%
The __________________is a positive integer (1, 2, 3, and so forth). It indicates the relative size of the orbital and therefore the relative distance
from the nucleus of the peak in the radial probability distribution plot.
principal quantum number (n)
The principal quantum
number specifies the energy level of the H atom: the ________ the n value, the ________
the energy level.
higher,
higher
The _________________is an integer from -l through 0 to
1+. It prescribes the three-dimensional orientation of the orbital in the space around
the nucleus.
magnetic quantum number (ml)
The ______________ is an integer from 0 to n -1. It is related to the shape of the orbital
angular momentum quantum number (l )
Give the name, magnetic quantum numbers, and number of orbitals for each sublevel with the given n and l quantum numbers:
(a) n=3, l=2
(b) n=2, l=0
(c) n=5, l =1
(d) n=4, l=3
(a) n=3
l=2
sublevel=3d
2-, -1, 0, +1, +2
kapoy type sa b, c, and d
An orbital with l=0 has a spherical shape with the nucleus at its
center
s orbital
An orbital with l=1 is called a__________________.
p orbital
An orbital with l=2 is called a__________________.
d orbital
In the special case of the H atom, the energy levels depend only on the___________.
n value
A wave can be thought of as a vibrating disturbance by which ________________ is transmitted.
energy
Wavelength is the ___________ between identical points on successive waves.
distance
The frequency is the __________ of waves that pass through a particular point in 1 second.
number
Another important property of waves is their speed which depends on the type of wave and the nature of the ________ through which the wave is traveling (for example air, water, or a vacuum).
medium
According to Maxwell’s theory, an electromagnetic wave has an _______________ field and a magnetic field component.
electric
Planck gave the name ___________ to the smallest quantity that can be emitted (or absorbed) in the form of electromagnetic radiation.
quantum
The photoelectric effect is a phenomenon in which electrons are ejected from the ____________ of certain metals when exposed to light with at least a minimum frequency, known as the threshold frequency.
surface
photons are particles of _____________ central to quantum theory, and Einstein’s explanation of the photoelectric effect established their existence and quantized energy.
light
particle-wave___________ is the concept in quantum mechanics that fundamental particles such as electrons and photons exhibit both particle-like and wavelike properties depending on the experimental conditions, challenging the traditional notions and distinct particles and waves.
duality
In a ____________ spectrum, all possible wavelengths within a given range are present, forming a smooth and connected distribution without any missing values.
continuous
Every element has a ___________ emission spectrum. The characteristic lines in atomic spectra can be used in chemical analysis to identify unknown atoms.
unique
Momentum is the ____________ of an object’s mass and its velocity.
product
The left side of the de Broglie’s equation involves the wave-like property of wavelength, whereas the right side makes references to the ____________ a distinctively particle-like property.
momentum
The most useful region of UV light for this purpose is ________.
200–400 nm
____________ has a slightly shorter wavelength (and, thus, higher frequency) than visible light.
Ultraviolet light
The energy difference between the two states depends on _________________.
the location of the electron
it requires light having a wavelength of < 200 nm
The promotion of electrons in sigma bonds and pi unconjugated bonds
The wavelength of UV light absorbed by a compound is often referred to as its___________.
lambda max
____________ absorb light in the UV region of the electromagnetic spectrum (200–400 nm).
Conjugated dienes and polyenes
As the number of conjugated pi
bonds _________, the energy difference between the ground and excited state __________, shifting the absorption to longer wavelengths.
increases,
decreases
With molecules having ___________ conjugated bonds, the absorption shifts from the UV to the ____________ and the compound takes on the color of those wavelengths of visible light it does not absorb.
eight or more,
visible region
The color that lycopene absorbs
blue-green region (470 nm)
Ultraviolet radiation from the sun is high enough in energy to cleave bonds, forming radicals that _____________________ and __________________.
can prematurely age skin and cause skin cancers
The UV region is subdivided into 3. Name the 3 regions and their specific wavelength range.
UV-A (320–400 nm),
UV-B (290–320 nm), and
UV-C (< 290 nm)
___________the highly conjugated colored pigment in the skin that serves as the body’s natural protection against the harmful effects of UV radiation.
melanin
Prolonged exposure to the sun can_________________________________________________________.
allow more UV radiation to reach your skin than melanin can absorb
A commercial sunscreen can offer added protection, however, because it contains __________________ that absorb UV light, thus shielding your skin (for a time) from the harmful effects of UV radiation.
conjugated compounds
2 conjugated compounds in used in sunscreens:
para-aminobenzoic acid and padimate O.
Conjugated compounds generally shield the skin from __________ radiation, but often have little effect on longer-wavelength __________ radiation, which does not burn the skin, but can still cause long-term damage to skin cells.
UV-B,
UV-A
Fortunately, much of the highest energy UV light _________is filtered out by the ozone layer, so that only UV light having wavelengths > 290 nm reaches the skin’s surface.
UV-C
______________ is used to calculate the wavelength
of maximum absorption of conjugated dienes and polyenes.
Woodward-Fieser rules
Write the Woodward-Fieser rules formula
Base value+ Sum of Substituents + Sum of Other Contributions
The ______________ depends upon whether the diene is a linear or heteroannular or transoid diene, or whether it is a
cyclic or homoannular diene
base value
This type of diene generally involves the attachement of two trans dienes together. Since the two double bonds attached are trans.
Transoid Diene / Heteroannular diene / linear diene
This type of diene involves the conjugation of two cis dienes. Since the double bonds are cis to each other, the molecule often tends to form a closed ring system.
Cisoid diene / Homoannular diene / cyclic diene
Only the substituents attached _______________ to the double bond diene systems can influence the ultraviolet visible absorption of the molecules.
directly
A____________ is a molecule which absorbs light at a particular wavelength and emit color as a result.
Chromophore
________________________ ultimately showed that it provides a better basis for describing, explaining, and predicting behavior at the atomic and molecular level.
Quantum mechanics
Quantum mechanics is based on several statements called __________________.
postulates
The behavior of electrons, by now known to have wavelike properties, can be described by a mathematical expression called a _______________________.
wavefunction
The wavefunction contains within it all possible information that can be known
about a __________________.
system
Wavefunctions are not arbitrary mathematical functions, but must satisfy
certain simple conditions. Name the 5 conditions.
(1) single valued
(2) continuous
(3) bounded
(4) differentiable
(5) square-integrable
_____________________ predicts values that agree with experimentally determined measurements.
Quantum mechanics
State the 1st postulate of Quantum Mechanics.
The state of a quantum mechanical system is completely specified by the wavefunction.
State the 2nd postulate of Quantum Mechanics.
To every observable in classical mechanics, there corresponds a linear, Hermitian operator in quantum mechanics.
State the 3rd postulate of Quantum Mechanics.
In any measurement of the observable associated with operator, the only values that will ever be observed are the eigenvalues.
A mathematical instruction
Operator
When an operator acts on a function
and produces the original function multiplied by any constant equation is referred to as an _______________________.
eigenvalue equation
The two basic operators are:
position operator,
linear momentum operator
In quantum mechanics, the eigenvalue equations that we will consider have __________________ as values of eigenvalues
real numbers
_______________________ are operators that always have real (nonimaginary) numbers as eigenvalues
Hermitian operators
All _________________ that yield quantum mechanical observables are Hermitian operators, because in order to be observed a quantity must be real.
operators
Hermitian operators are named after ______________________, a nineteenth century French mathematician.
Charles Hermite
