Ch. 7 Quantum Theory and the Electronic Structure of Atoms
Speed of any form of radiation will be given by the product of_
-the wavelength and the frequency (m/cycle) X (cycles/s)= m/s (unit of speed)
what are the shortest waves? (include their frequency)
-they have the highest frequency -gamma rays
energy is a certain_. why?
-wave -when it leaves it source it affects the space around of it in an osilation motion, which we call waves
what formula describe all electromagnetic radiation?
All electromagnetic radiation wavelength x frequency = c (speed of light)
what Planck could not explain about his theory?
At the time Planck presented his theory, he could not explain why energies should be fixed or quantized in this manner (hv, 3 hv, 2 hv....)
how to determine the speed of the wave? (include the symbol for it?) (equation)
The speed (u) of the wave = wavelength x frequency
describe the frequency and energy characteristics when wavelength is shorter?
Wavelength is shorter=higher frequency=higher energy
light passing through 2 adjacent slits
constructively amplitudes add, waves in phase destructive amplitudes cancel, waves out of place
wave
continuously repeating change (oscillation) in matter or in a physical fiels
electric field
electrically charged particles experience a force
Entire range of wave lengths is called _
electromagnetic spectrum
radiation is a form of_
energy
what is a property of matter?
energy
electromagnetic radiation
energy in the form of oscillation in matter or in a physical field
according to the quantum theory how energy is emitted? (in terms of hv)
energy is always emitted in integral multiples of hv (ex: hv, 2hv, 3hv...) but never 1.67hv, or 4.89 hv
planck basic idea
energy of an atom is quantized; can only contain certain fixed quantities not continuous; each change in energy results from gain or loss of quanta (packet of energy)
all em radiation consists of
energy propagated by electric and magnetic fields
electric and magnetic fields alternately
increase and decrease in intensity as they move
electromagnetic radiation
is the emission and transmission of energy in the form of electromagnetic waves
what is another important property of the waves?
is their speed
what the speed of a wave depend on? (2)
it depends on the type of wave and the nature of the medium through which the wave is traveling (for example, air, water, or a vacuum)
wavelength units?
it is usually expressed in units of meters, centimeters, or nanometers
threshold frequency
light must have a minimum frequency or not current flows
electrons determine
many of the chemical and physical properties
absence of time lag
regardless of intensity, no time lag with certain lights because intensity doesn't matter just frequency of light
radiation with high frequency has
short wavelength and high energy
emission of electrons depends on
single photon having sufficient energy to dislodge a single electron
diffraction
spreading out of waves when they encounter an obstruction or opening the size of the wavelenght
what is the relation between frequency and the energy associated with radiation?
the higher the frequency, the more energetic the radiation
properties of atoms and molecules are not governed by_
the same physical laws as larger objects
quantum mechanics
theory that explains the behavior of the extremely small
in vacuum all types of radiation
travel at speed of light
hertz
unit of frequency
magnetic field
does no worked on charged particle; where an area object exhibits a magnetic influence
particles vs. waves
don't undergo refraction when passing through dif mediums; in slit experiment pass straight through
Now compare 2 beams of light having the same frequency (greater than the threshold frequency) but different intensities when directed against the metal
-The more intense beam of light consists of a larger number of photons; consequently, it ejects more electrons from the metal's surface than the weaker beam of light -Thus, the more intense the light, the greater the number of electrons emitted by the target metal -The greater the frequency of the light, the greater the kinetic energy of the ejected electrons
what Max Planck did? (what he did, what he discovered, what physicist assumed in that time?) How he called his theory?
-While analyzing the data on radiation emitted by solids heated to various temperatures, Planck discovered that atoms and molecules emit energy only in certain discrete quantities, or "quanta" -Physicists had always assumed that energy is continuous and that any amount of energy could be released in a radiation process -His theory was called: Plank's quantum theory
photoelectric effect
-a phenomenon in which electrons are ejected from the surface of certain metals exposed to light of at least a certain minimum frequency, called the threshold frequency
what did Maxwell's theory stated?
-an electromagnetic wave has an electric field component and a magnetic field component -these 2 components have the same wavelength, frequency, and amplitude, and hence the speed, but they travel in mutually perpendicular planes (oscillate in 2 mutually perpendicular planes)
how atoms are arranged in solids (especially metals)? who gave an explanation to this arrangement (explain what he said)?
-atoms are fixed in place and they vibrate or oscillate at place at frequency depends on particular metal that you are dealing with -Plank's equation explained the behavior of solid metals (E=h X frequency) -He had to embrace the odd idea that atoms in solids will have certain fixed amount of energy (quantize the energy) -Fixed defined amount of energy to metals (positive values only)
starting with this hypothesis, Planck had no trouble correlating the experimental data for_. They all supported the_
-emission by solids over the entire range of wavelengths -They all supported the quantum theory
what is the value of Planck's constant? (include symbol)
-h 6.63 X 10⁻³⁴ J∙s
the _ the frequency is the_the energy associated with the light. what happens in the opposite case?
-higher -greater -the lower frequency is the lower energy associated with the light
The number of electrons ejected (in the photoelectric effect) is proportional to the_, but the _were not. Below the_no electrons were ejected no matter how intense is the light
-intensity (or brightness) of the light -energies of the ejected electrons -threshold frequency
what is the significance of Maxwell's theory?
-is that it provides a mathematical description of the general behavior of light -In particular, his model accurately describes how energy in the form of radiation can be propagated through space as vibrating electric and magnetic fields
amplitude
-is the vertical distance from the midline of a wave to the peak or trough; brightness of wave
what the amplitude determines of light? what about colors?
-it determines the intensity of light -the farther it is from the middle, the brighter the light will be -the closer to the middle, the duller the light will be -differentiate between colors by amplitude of wavelength
frequency units?
-it is measured in hertz (Hz), where 1Hz=1cycle/s 1/s or s^-1 (1 per second) ex: 25/s or 25 s^-1 (25 per second)
wavelength (symbol, definition, units)
-lambda symbol -is the distance between identical points on successive waves. -distance in one cycle (m/cycle)
electromagnetic waves travel at what speed? (include name and symbol) in which medium? how it travels in another mediums?
-Speed of light (c) in vacuum = 3.00 x 10⁸ m/s -This speed differs from one medium to another, but not enough to distort our calculations significantly
what is the relation between frequency and wavelength?
-The higher the frequency, the shorter the wavelength will be -If reduce its wavelenght by ½, its frequency will increase by factor of 2 -Reciprocal relationship between frequency and wavelength
wavelength lambda
distance between any two adjacent identical points of wave
what determines the amount of energy a compound has?
each compound has certain amount of energy that depends on the way it is compose
how gamma rays result?
from changes within the nucleus of the atom
How Einstein called the particles of the stream if light?
photons
electromagnetic radiation is emitted as well as absorbed in the form of_
photons
what type of light is white light?
polychromatic light
Planck's theory is called_
quantum theory
what are the longest electromagnetic waves?
radio waves
what is the visible light color with the highest energy?
violet
By using Einstein theories at the time, light has both_ (2 natures)
wave nature particle nature
visible light ranges from a_
wavelength of 400 nm to 700 nm
visible light range
400-750 nm
electromagnetic spectrum
range of frequencies or wavelengths of electromagnetic radiation
what is the visible light color that has the lowest energy?
red
what are other examples that can be quantized besides energy? (include how they are related)
*There could be only whole-number multiples* -electric charge of electrons -Matter (number of electrons, protons, and neutrons, and atoms must be integers) -monetary system (penny) -living systems (born organisms)
which rays have the shortest wavelength? what about its frequency?
-gamma rays -highest frequency
the energy (E) of a single quantum of energy is given by_ ( 2 formula)
E=hv E= energy h= Planck's constant v= frequency of radiation E=h (c/wavelength) c= speed of light
what happens if we pass light through a prism?
If you pass white light through prism, the light separates into 7 colors
who solved the problem of heated solids?
Plank
polychromatic light
Light of many different colors
monochromatic light
Light of specific color (single)
The new era of physics started in 1900 with who?
Max Planck
how are the shorter, visible light waves produced?
by the motions of electrons within atoms and molecules
what is the magnitude of the speed of light?
c= 3.00 X 10⁸ m/s
work function
a certain amount of energy is needed to eject the electron
wave
a vibrating disturbance by which energy is transmitted
electromagnetic wave
a wave that has an electric field component and a mutually perpendicular magnetic field component
wave theory associates energy of light with
amplitude
how the various types of electromagnetic radiation differ? (2)
by having different wavelength and frequency
where are radio waves emitted?
by large antennas, such as those by broadcasting stations
what the measurements taken during the 19th century showed about how much energy can an object emit? what theory and law could not explain this?
measurements taken in the latter part of the nineteen century showed that the amount of radiant energy emitted by an object at a certain temperature depends on its wavelength -Attempts to account for this dependence in terms of established wave theory and thermodynamic laws were only partially successful -Some theories could explain the short wavelengths dependence and other the long wavelengths dependence, but seemed that something fundamental was missing of the classical physics laws
speed of wave changes when
moves from different medium; refraction through water
the wavelength of electromagnetic waves is usually given in which units?
nanometers (nm)
intensity relates to
number of photons
frequency
number of wavelengths of a wave that pass a fixed point in one unit of time usually a second
photon
particle of light
what are the 2 parts of the wave?
peaks troughs
early ideas of quantum theory led to a new era in physics called_
quantum mechanics
threshold frequency
-1 type of energy will make electrons break free and that is the minimum energy need to put (certain minimum frequency)
what mystery Albert Einstein solved? (regarding the quantum theory)
-Albert Einstein used the theory to solve another mystery of physics, the photoelectric effect
what was well established in the 19th century? what was not known?
-Beginning of 19th century, people knew energy (radiation) traveled in waves -relates with intensity of light and speed of light (properties of wave length) -know speed of light -wave theory was very established -Mysteries that the wave theory could not explain
what was the earlier attempt to explain the way atoms and molecules are? (describe it, what physicists could do about this and what they could not do)
-By assuming that molecules behave like rebounding balls, physicists were able to predict and explain some macroscopic phenomena, such as the pressure exerted by a gas -However, this model did not account for the stability of molecules; it could not explain the forces that hold atoms together
how the electromagnetic radiation travels?
-Combination of movements, they oscillate and move through space in a very synchronized manner→thrust contacts with crest -they oscillate in 2 mutually perpendicular planes -All radiation travel with speed of light
who's explanation of what is another step toward the development of the quantum theory? To explain experimental observations, he suggested that _
-Einstein's explanation of the photoelectric effect -Einstein suggested that light behaves like a bundle of particles called photons
explain the particle-wave duality (include the dilemma of this)
-Einstein's theory of light posed a dilemma for scientists -On the one hand, it explains the photoelectric effect satisfactorily -On the other hand, the particle theory of light is not consistent with the known wave behavior of light -The only way to resolve the dilemma is to accept the idea that light possesses both particle-like and wavelike properties -Depending on the experiment, the light behaves either as a wave or as a stream of particles. This concept is called the particle-wave duality
describe how electrons are found in a metal and what is required to remove them from the metal?
-Electrons are held in a metal by attractive forces, and so removing them from the metal requires light of a sufficiently high frequency (which corresponds to sufficiently high energy) to break them free -Shining a beam of light onto a metal surface can be thought of as shooting a beam of particles (photons) at the metal atoms -If the frequency of photons is such that hv is exactly equal to the energy to knock the electrons be knocked loose, but they will also acquire some kinetic energy -This situation is summarized by the equation hv= KE (kinetic energy of ejected electron) + W (work= measure how strong electrons are held in the metal) -The more energy the photon (the higher frequency), the greater the kinetic energy of the ejected electron
what were the 3 problems that could not explained by physicists?
-Heated solids -photoelectric effect -line spectra of atoms
explain in more detail the mystery of the heated solids and what wave theory could not explain.
-If have chunk of metal, if were to heat it, when temperature get to 1000K it begins to emit visible light (dull red radiation) -when continue heat it nothing happens until 5000K -between 1000 and 1500 continues dull red -15000k and 20000k it is pink color -20000k it begins to emit quite light -Wave theory could not explain that because amount of energy changes continuously→there should be a change of the color of light that the object emits but the object did not change of color until specific amount of K
waves are characterized by their _(3)
-Length (wavelength) -height (amplitude) -frequency
what James Clerk Maxwell proposed?
-Maxwell (1873), proposed that visible light consists of electromagnetic waves
How Planck solved the problem of heated solids? (include what the classical physics thought about this phenomena)
-Planck solved the problem with an assumption that departed drastically from accepted concepts -Classical physics assumed that atoms and molecules could emit (or absorb) any arbitrary amount of radiant energy -Planck said that atoms and molecules could emit (or absorb) energy only in discrete quantities, like small packages or bundles -Planck gave the name quantum -Energy (light) is emitted or absorbed in discrete units (quantum).
Describe the machine that studies photoelectric effect?
-light of certain frequency falls on a clean metal surface -Ejected electrons are attracted toward the positive electrode -The flow of electrons is registered by a detecting meter -Light meters used in cameras are based on the photoelectric effect -plate of metal of potassium and put it in chamber in vacuum= 2 wires that are connected to opposite poles to link to a meter -when you shine a monochromatic light on metal(light of 1 color) let electrons break free of the metal -so electrons very quickly attracted to the positive charge and current will flow
quantum
-name given by Planck -the smallest quantity of energy that can be emitted (or absorbed) in the form of electromagnetic radiation -discrete units
frequency (symbol, definition, and unit)
-nu (v) -is the number of waves that pass through a particular point in 1 second (Hz = 1 cycle/s). -number of waves that pass a specific point in space per unit time (seconds)
which wave has the longest wavelength? what about its frequency?
-radio waves -lowest frequency
what is the visible light color that has the longest wavelength? (indicate the value)
-red 700 nm
analyze: speed of wave= wavelength X frequency
-the wavelength expresses the length of a wave, or distance/wave -the frequency indicates the number of these waves that pass any reference point per unit of time, or waves/time -Thus, the product of these terms results in dimensions of distance/time, which is speed: (distance/time)= (distance/wave) X (waves/time)
wavelength can be measured between_(3)
-two troughs -two peaks -any 2 point that are identical
what are the 3 electromagnetic waves have a high-energy radiation? why?
-ultraviolet radiation -X rays -gamma rays -because the higher the frequency, the more energetic the radiation
what is the visible light wave color that has the shortest wavelength? (indicate the value)
-violet 400 nm
what are 3 types of waves?
-water waves -sound waves -light waves
the photoelectric effect could not be explained by the_ (explain why). However, Einstein made an extraordinary assumption_
-wave theory of light. According to wave theory, no matter what type of light shine to metal electrons will break free. However, electrons will break free only with specific light. People tried to exposed the metal with a lower light→regardless of what they did only one light will make the electrons eject from the plate and was the buttle light(?) -He suggested that a beam of light is really a stream of particles -Using Planck's quantum theory of radiation as starting point, Einstein deduced that each photon must possess energy E, given by the equation E= hv (where v is the frequency of light) -It is light itself that it is quantized→he said light exists as particles because those particles have specific electromagnetic energy associated with them -He said that electron will be ejected only if the light shine to metal has specific frequency (threshold frequency)
what are the 3 properties of waves?
-wavelength -frequency -amplitude
each type of radiation is spread over a specific_(2) in the electromagnetic spctrum
-wavelengths and frequencies
Describe what happen when the light of specific frequency is directed toward the metal at the molecular level
-when photon of light hits the electrons, it becomes pure energy, electron absorbs energy and break energy bonds and we say photon is absorbed -Photon will be converted into energy when hit electron that is sufficient to make the electron to break connections to break free
what happen when a solid is heated? (give 2 examples)
-when solids are heated, they emit electromagnetic radiation over a wide range of wavelengths -ex: dull red of electric heater and bright white of a tungsten ligthbulb
can you list from highest to lowest energy radiation in the electromagnetic spectrum?(7)
1. gamma rays 2. X rays 3. Ultra violet rays 4. Visible light 5. Infrared 6. Microwave 7. Radio waves
conversion factor of 1 nanometer to meter and viceversa?
10^9nm= 1m 1nm= 10^-9 m
