Classical physics predicts that
accelerating charged particles should emit radiation
. If this happened, the loss of energy should be accompanied by a spiraling of the electron into the atomic nucleus (akin to the fate of satellites that encounter the atmosphere in low Earth orbit.
What did classical physics predict about the structure of the atom?
Classical physics predicts that
accelerating charged particles should emit radiation
. If this happened, the loss of energy should be accompanied by a spiraling of the electron into the atomic nucleus (akin to the fate of satellites that encounter the atmosphere in low Earth orbit.
Why can’t classical physics explain the photoelectric effect?
The photoelectric effect has three important characteristics that cannot be explained by classical physics: (1)
the absence of a lag time
, (2) the independence of the kinetic energy of photoelectrons on the intensity of incident radiation, and (3) the presence of a cut-off frequency.
What did Thomson conclude about the particles in cathode rays?
Thomson’s experiments with cathode ray tubes showed that
all atoms contain tiny negatively charged subatomic particles or electrons
.
What did Bohr contribute to the atom?
Bohr was the first to discover that
electrons travel in separate orbits around the nucleus and that the number of electrons in the outer orbit
determines the properties of an element. The chemical element bohrium (Bh), No. 107 on the periodic table of elements, is named for him.
Why does classical physics predict that atoms should collapse?
Why does classical physics predict that atoms should collapse? According to Maxwell’s theory,
accelerating charged particles should radiate energy in the form of electromagnetic waves
. So, according to the classical physics, an electron accelerating around a nucleus should radiate energy continuously.
What were the failures of classical physics?
If you look at most of the “equations” above, you will find Planck’s constant, h. This is the trademark of “modern physics.” The failure of classical physics to explain
blackbody radiation, the photoelectric effect, and the hydrogen atom
ultimately demolished the foundations of classical physics.
Why was the classical theory a failure?
Classical wave theory cannot explain the first 3 observations of photoelectric effect. Since energy of the wave is dependent on the square of its amplitude, the classical wave theory predicts that if sufficiently intense light is used,
the electrons would absorb enough energy to escape
.
How did Thomson Discover electron?
Thomson discovered the electron by
experimenting with a Crookes, or cathode ray, tube
. He demonstrated that cathode rays were negatively charged. … Thomson realized that the accepted model of an atom did not account for negatively or positively charged particles.
Why did Thomson think that electrons are in all types of atoms?
Thomson Discovers Electrons
He thought they
were the smallest particles of matter
, which could not be broken down into smaller particles. He envisioned them as solid, hard spheres. … Thomson discovered that there are smaller particles within the atom.
What 3 things did Bohr’s model propose about electrons?
Bohr’s model of the hydrogen atom is based on three postulates: (1) an electron moves around the nucleus in a circular orbit, (2) an electron’s angular momentum in the orbit is quantized, and (3)
the change in an electron’s energy as it makes a quantum jump from one orbit to another is always accompanied by the
…
What was Bohr’s theory?
In 1913, Niels Bohr proposed a
theory for the hydrogen atom
, based on quantum theory that some physical quantities only take discrete values. Electrons move around a nucleus, but only in prescribed orbits, and If electrons jump to a lower-energy orbit, the difference is sent out as radiation.
How did JJ Thomson know the electron was negative?
In order to determine if the cathode ray consisted of charged particles, Thomson used magnets and charged plates to deflect the cathode ray. He observed that
cathode rays were deflected by a magnetic field in the same manner as a wire carrying an electric current
, which was known to be negatively charged.
Which statement did Niels Bohr make about atoms?
Niels Bohr proposed a model of
the atom in which the electron was able to occupy only certain orbits around the nucleus
. This atomic model was the first to use quantum theory, in that the electrons were limited to specific orbits around the nucleus.
How can we explain why electrons don’t spiral into the attracting nucleus quizlet?
How can we explain why electrons don’t spiral into the attracting nucleus?
Electrons behave like a standing wave, not like a charged particle
in an orbit that would lose energy and emit radiation. … The average distance of the cloud from the nucleus is close to that of the radius of the Bohr orbit.
What does Bohr’s correspondence principle say about quantum mechanics versus classical mechanics?
If quantum mechanics were to be applicable to macroscopic objects, there must be some limit in which quantum mechanics reduces to classical mechanics. Bohr’s correspondence principle
demands that classical physics and quantum physics give the same answer when the systems become large
.
How does the amplitude of a matter wave relate to probability?
How does the amplitude of a matter wave relate to probability? The amplitude of a matter wave is called
its wave function
, represented by the symbol psi . Where psi is large, the particle (or other material) is more likely to be found. Where psi is small, the particle is less likely to be found.
What are under classical physics?
Classical physics involves
classical mechanics
(the study of the movement of fluids and particles), thermodynamics (the study of temperature and heat transfer), and electromagnetism (the study of electricity, magnets, and electromagnetic waves).
What is classical theory in physics?
In the context of quantum mechanics, classical theory refers
to theories of physics that do not use the quantisation paradigm
, which includes classical mechanics and relativity. Likewise, classical field theories, such as general relativity and classical electromagnetism, are those that do not use quantum mechanics.
Which theory could not be explained by the classical mechanics theory?
Classical mechanics was unable to explain certain phenomena:
black body radiation
, the photoelectric effect, the stability of atoms and molecules as well as their spectra. Quantum mechanics, created mainly by Werner Heisenberg and Erwin Schrödinger, explained these effects.
What are the drawbacks of classical mechanics?
Classical physics
fails to explain the motion of heavenly bodies in strong gravitational fields
e.g. motion of mercury at its perihelion and also it cannot explain bending of light in vicinity of massive gravitational bodies, gravitational lensing etc.
Why do we need classical mechanics?
Classical mechanics provides
extremely accurate results
when studying large objects that are not extremely massive and speeds not approaching the speed of light. … To describe velocities that are not small compared to the speed of light, special relativity is needed.
What is classical wave theory?
According to the classical wave theory of light,
the intensity of the light determines the amplitude of the wave
, and so a greater light intensity should cause the electrons on the metal to oscillate more violently and to be ejected with a greater kinetic energy.
Who discovered electron flow?
150 years later in 1897,
JJ Thomson
would discover the electron and the fact that current flowed from the negative of a power supply to the positive of a power supply. This is what we now know as electron current flow.
Who proved the existence of electrons?
Their work culminated in the discovery by
English physicist J.J. Thomson
of the electron in 1897. The existence of the electron showed that the 2,000-year-old conception of the atom as a homogeneous particle was wrong and that in fact the atom has a complex structure.
What did Millikan discover about the electron?
Robert Millikan’s oil-drop experiment. By comparing applied electric force with changes in the motion of the oil drops, he was able to determine the electric charge on each drop. He found that
all of the drops had charges that were simple multiples of a single number
, the fundamental charge of the electron.
What did Thomson discover about the atom?
Thomson announced his discovery that
atoms were made up of smaller components
. This finding revolutionized the way scientists thought about the atom and had major ramifications for the field of physics. Though Thompson referred to them as “corpuscles,” what he found is more commonly known today as the electron.
Why did JJ Thomson conclude that the particles were negatively charged?
Thomson found that
the path taken by the cathode ray could be bent towards a positive metal plate, and away from a negative metal plate
. As a result, he reasoned that the particles in the cathode ray were negative.
What did James Chadwick discover?
In 1932, Chadwick made a fundamental discovery in the domain of nuclear science: he proved the existence
of neutrons
– elementary particles devoid of any electrical charge.
What findings led Thomson to infer that particles that are smaller than atoms do exist?
Hypothesized that most of an atoms mass and all its positive charge were contained in a small nucleues. What findings led Thomson to infer that particles that are similar than atoms do exist?
Since electrons came from every kind of cathode material, Thomson inferred
that they are a part of all atoms.
What is an interesting fact about JJ Thomson?
J. J. Thomson took science to new heights with his
1897 discovery of the electron – the first subatomic particle
. He also found the first evidence that stable elements can exist as isotopes and invented one of the most powerful tools in analytical chemistry – the mass spectrometer.
What is James Chadwick atomic theory?
Chadwick is best known for his
discovery of the neutron
in 1932. A neutron is a particle with no electric charge that, along with positively charged protons, makes up an atom’s nucleus. … In this way, Chadwick’s findings were pivotal to the discovery of nuclear fission, and ultimately the development of the atomic bomb.
Why was Bohr model proposed by Bohr?
Bohr Atomic Model : In 1913 Bohr proposed his
quantized shell model of the atom to explain how electrons can have stable orbits around the nucleus
. … To remedy the stability problem, Bohr modified the Rutherford model by requiring that the electrons move in orbits of fixed size and energy.
What are the most important points of the Bohr theory?
Main Points of the Bohr Model
Electrons orbit the nucleus in orbits that have a set size and energy
. The energy of the orbit is related to its size. The lowest energy is found in the smallest orbit. Radiation is absorbed or emitted when an electron moves from one orbit to another.
What four assumptions did Bohr make about the electronic structure of the atom?
According to Bohr: 1) Electrons in atoms orbit the nucleus, 2) The electrons can only orbit stably, without radiating, in certain orbits, and 3)
Electrons can only gain and lose energy by jumping from one allowed orbit to another
.
What did Bohr say about electrons?
Bohr proposed
that electrons do not radiate energy as they orbit the nucleus, but exist in states of constant energy which he called stationary states
. This means that the electrons orbit at fixed distances from the nucleus (see Figure below).
How do electrons move in Bohr model?
In the Bohr model of the atom, electrons
travel in defined circular orbits around the nucleus
. … Electrons can jump from one orbit to another by emitting or absorbing energy.
What was Niels Bohr’s key hypothesis about the behavior of electrons in atoms that he formulated to explain the discrete pattern of atomic spectra?
He postulated that
the angular momentum of the electron is quantized—i.e., it can have only discrete values
. He assumed that otherwise electrons obey the laws of classical mechanics by traveling around the nucleus in circular orbits. Because of the quantization, the electron orbits have fixed sizes and energies.
What did Werner Heisenberg discover?
Werner Heisenberg discovered
the uncertainty principle
, which states that the position and the momentum of an object cannot both be known exactly.
How did Bohr make use of the concept of quantum in explaining the state of electrons in the atom?
Bohr explained that electrons can be moved into different orbits with the addition of energy.
When the energy is removed, the electrons return back to their ground state, emitting a corresponding amount of energy—a quantum of light
, or photon. This was the basis for what later became known as quantum theory.
How does Bohr’s model explain atomic spectra?
Bohr’s model explains the spectral lines of the
hydrogen
atomic emission spectrum. While the electron of the atom remains in the ground state, its energy is unchanged. When the atom absorbs one or more quanta of energy, the electron moves from the ground state orbit to an excited state orbit that is further away.
