What occurs when an atom absorbs a photon with precise energy?
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It can transition to a higher energy state.
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What occurs when an atom absorbs a photon with precise energy?
It can transition to a higher energy state.
What is the Rydberg formula used for?
To describe the spectrum of the hydrogen atom.
What did Louis de Broglie argue about the electron in its circular orbit?
The electron must be seen as a particle wave.
What did J. J. Thomson discover in 1897?
That atoms contain negatively charged constituents (electrons) that are identical for all atoms.
Why are atoms electrically neutral?
Because they contain both negatively charged electrons and some positive charge to neutralize them.
What is the principal quantum number denoted by?
n.
What is a spectral series?
Sets of spectral lines that exhibit a regular pattern.
What does the negative sign in the electrostatic potential energy (U) signify?
It signifies that the electrostatic force is in the –r direction.
What is the shortest wavelength in the Balmer series?
364.6 nm.
What contradiction arises from the classical electromagnetic theory regarding emitted light from electrons?
It predicts a continuous spectrum instead of the observed line spectrum.
Who is Niels Bohr and what did he contribute to atomic theory?
A Danish physicist who explained the spectrum of the hydrogen atom based on quantum ideas.
What principle did Niels Bohr propose to clarify conceptual problems in quantum mechanics?
The complementary principle.
What does the Bohr model primarily involve in its formulation?
The electrical force between the positively charged nucleus and the electron.
What are the names of the series identified for the hydrogen atom?
Lyman, Balmer, Paschen, Brackett, and Pfund series.
What do dark spectral absorption lines indicate when photons pass through a rarefied gas?
The frequencies that have been absorbed by the atoms of the gas.
What is the quantum condition proposed by Bohr for the angular momentum of the electron?
m v_n r_n = nh/2π.
What is concentrated in the nucleus according to Rutherford's model?
The entire positive charge and most of the mass of the atom.
What happens when an alpha-particle comes near a nucleus?
It is scattered through a large angle due to the intense electric field.
What is indicated by the integers n_f and n_i in the Rydberg formula?
They represent different atomic energy levels.
What type of radiation do condensed matter and dense gases emit?
Electromagnetic radiation with a continuous distribution of several wavelengths.
How much energy is required to separate a hydrogen atom into a proton and an electron?
13.6 eV.
What are the wavelengths of the first four lines in the Lyman series of the hydrogen spectrum?
1218 Å, 1028 Å, 974.3 Å, and 951.4 Å.
What experiment did Apollo astronauts conduct with lasers on the moon?
They placed a mirror on the moon to reflect a laser beam back to Earth for distance measurement.
What did Rutherford estimate regarding the atomic nucleus?
The approximate size of the nucleus.
What is the relationship between wavelength and frequency in the context of the Balmer formula?
c = νλ, where c is the speed of light.
What new theory is required for understanding complex atoms beyond the Bohr model?
Quantum Mechanics.
What does the Rutherford model of the atom assume?
The atom consists of a central nucleus and revolving electrons, similar to a sun-planet system.
What is the relationship between the frequency of the emitted photon and the energy states?
hν = Ei - Ef, where Ei and Ef are the energies of the initial and final states.
What happens when an electron transitions from a higher energy state to a lower energy state?
Photons are emitted, producing spectral lines.
What significant evidence accumulated by the nineteenth century regarding matter?
Evidence in favor of the atomic hypothesis.
What assumption is made in the derivation of Eqs. (12.17) – (12.19)?
That the electronic orbits are circular.
What is the process called when an electron transitions from a lower energy state to a higher energy state?
Absorption.
What are the expressions for kinetic energy (K) and electrostatic potential energy (U) of the electron in a hydrogen atom?
K = 2 2 0 1 mv^2 and U = -2 8 4 e^2/r.
What did Rutherford's experiments with alpha-particles lead to?
The birth of Rutherford’s planetary model of the atom.
What aspect of hydrogen's emission spectrum does the Bohr model fail to explain?
The relative intensities of the frequencies.
In what year was Bohr awarded the Nobel Prize in Physics?
What is the value of the Bohr radius (a₀)?
5.29 × 10⁻¹¹ m.
What is the term used for the wave-like description of electrons in quantum mechanics?
Orbital.
What limitation does the Bohr model have regarding multi-electron atoms?
It cannot be extended to atoms with more than one electron, such as helium.
What is the radius of the gold nucleus compared to the calculated distance of closest approach?
The radius of the gold nucleus is less than 3.0 × 10⁻¹⁴ m, while the actual radius is 6 fm.
What is the formula for the Lyman series?
R(1/n²) for n = 2, 3, 4...
What is the formula for the force on an α-particle in relation to the nucleus?
F = (2)(Ze^2)/r^2, where r is the distance between the α-particle and the nucleus.
What force keeps the electrons in their orbits according to the Rutherford model?
The electrostatic force of attraction between the electrons and the nucleus.
What did C. J. Davisson and L. H. Germer experimentally verify?
The wave nature of electrons.
Who made modifications to the atomic model by incorporating quantum hypothesis?
Niels Bohr.
What defines the stable orbits according to Bohr's second postulate?
The angular momentum is an integral multiple of h/2π.
What was the thickness of the gold foil used in the experiment?
2.1 × 10 –7 m.
What happens to an accelerating charged particle according to classical electromagnetic theory?
It emits radiation in the form of electromagnetic waves.
What is the value of the Rydberg constant R obtained from the theoretical formula?
R = 1.03 × 10^7 m⁻¹.
What series corresponds to transitions where n_f = 2?
The Balmer series.
What is the spectrum called when white light passes through a gas and dark lines appear?
Absorption spectrum.
What was the first model of the atom proposed by J. J. Thomson?
The Plum Pudding Model.
What is the overall charge of an atom?
Electrically neutral, containing equal amounts of positive and negative charges.
Why do most alpha-particles pass through a thin metal foil?
Because most of an atom is empty space.
What is the total energy (E) of the electron in a hydrogen atom?
E = K + U = -2 0 8 e^2/r.
How does quantum mechanics differ from the Bohr model in describing electron motion?
Quantum mechanics describes electron motion in terms of probabilities rather than definite paths.
How does laser light differ from light emitted by ordinary sources?
Laser light has better phase correlation and a more uniform wavelength.
Who performed the experiments suggested by Rutherford in 1911?
H. Geiger and E. Marsden.
In which region is the Lyman series found?
Ultraviolet region.
What is the expression for the total energy of the electron in the hydrogen atom?
Eₙ = - (2.18 × 10⁻¹⁸ J)/n².
What happens to the spacing between lines in the hydrogen spectrum as the wavelength decreases?
The lines appear closer together and are weaker in intensity.
What does the successful reflection of a laser beam from the moon allow scientists to measure?
The extremely small divergence of a laser beam and the distance of the moon from the Earth.
What does the negative sign in the total energy of an electron indicate?
The electron is bound to the nucleus.
What is Bohr's quantization condition?
Angular momentum L = nh/2π, where n is an integer called a quantum number.
What was Bohr's first postulate about electrons in an atom?
An electron can revolve in certain stable orbits without emitting radiant energy.
What does the comparison of atomic and solar system dimensions imply about atomic structure?
It implies that an atom contains a much greater fraction of empty space than our solar system does.
What is the relationship between the energy levels and the quantum number n in a hydrogen atom?
As n increases, the energy levels become less negative, indicating higher energy states.
What does the emission line spectrum of atomic hydrogen consist of?
Bright lines on a dark background.
What can the study of emission line spectra serve as for gases?
A type of 'fingerprint' for identification.
What is the relationship between the circumference of the electron's orbit and its wavelength?
2 π r_n = n λ, where n = 1, 2, 3...
What limitation does the Bohr model have regarding multi-electron atoms?
It does not include the electrical forces between electrons.
What does the agreement between theoretical and experimental values of the Rydberg constant confirm?
It provides a direct confirmation of Bohr's model.
Who first observed the Balmer series in the hydrogen spectrum?
Johann Jakob Balmer.
What is the formula for the size of the innermost orbit (n=1)?
r₁ = (2h²)/(me²), known as the Bohr radius (a₀).
What is the wavelength of the Hα line in the Balmer series?
656.3 nm.
What is the charge of an alpha-particle?
2 e (two units of positive charge).
What is the atomic number of gold (Au)?
What causes the electromagnetic radiation emitted by matter?
Oscillations of atoms.
What is the calculated orbital radius of the electron in a hydrogen atom?
5.3 × 10^(-11) m.
What laws are used to compute the trajectory of an alpha-particle during scattering?
Newton’s second law of motion and Coulomb’s law for electrostatic force of repulsion.
What type of spectrum does an atomic gas or vapor emit when excited?
An emission line spectrum.
What energy is required to remove the electron from the hydrogen atom?
Energy is required to move the electron to a distance infinitely far from the nucleus.
What does Bohr's third postulate state about electron transitions?
An electron can transition between non-radiating orbits, emitting a photon with energy equal to the energy difference.
How were the α-particles collimated before hitting the gold foil?
By passing through lead bricks.
How many α-particles deflect by more than 90º?
About 1 in 8000.
What is the energy of the ground state (n=1) of a hydrogen atom?
-13.6 eV.
What would happen to an electron in an atom according to classical electromagnetic theory?
It would spiral inward and eventually fall into the nucleus.
What did Rutherford's experiments suggest about the structure of the atom?
The entire positive charge and most of the mass are concentrated in the nucleus, with electrons orbiting at a distance.
What is the relation between the orbit radius and the electron velocity in a hydrogen atom?
The relation is given by the equation 2 2 0 4 e r mv.
What did Johann Jakob Balmer establish in 1885?
A simple empirical formula for the wavelengths of lines emitted by atomic hydrogen.
What is the de Broglie wavelength of an electron moving in the n-th orbit?
λ = h/p, where p is the electron's momentum.
How did Thomson describe the arrangement of charges in his model?
The positive charge is uniformly distributed throughout the atom, with electrons embedded like seeds in a watermelon.
What is the acronym LASER stand for?
Light Amplification by Stimulated Emission of Radiation.
What was a major limitation of Rutherford's nuclear model?
It could not explain why atoms emit light of only discrete wavelengths.
What are hydrogenic atoms?
Atoms consisting of a nucleus with positive charge +Ze and a single electron.
What are the two main difficulties of Rutherford's nuclear model?
(a) It predicts atoms are unstable due to spiraling electrons, contradicting matter's stability. (b) It cannot explain the characteristic line spectra of different elements.
For which type of atoms is the Bohr model valid?
Only one-electron atoms/ions.
How does the mass of the gold nucleus compare to that of an alpha-particle?
The gold nucleus is about 50 times heavier than an alpha-particle.
What does the Rutherford nuclear model depict?
An atom as a positively charged nucleus surrounded by revolving electrons in stable orbits.
What is the relationship between energy and the principal quantum number n in the Bohr model?
Energy depends only on the principal quantum number n for one-electron atoms/ions.
Which elements have spectra that can be represented by simple formulas?
Hydrogen, singly ionized helium, and doubly ionized lithium.
What happens to an α-particle in a head-on collision with the nucleus?
The α-particle rebounds back with an angle θ ≈ π.
What type of particles were directed at the gold foil in the Geiger-Marsden experiment?
5.5 MeV α-particles emitted from a 21483 Bi radioactive source.
What does the solid curve in the experiment's graph represent?
The theoretical prediction based on the assumption of a small, dense, positively charged nucleus.
What is the quantum number for the satellite motion calculated in the example?
5.3 × 10^45.
What is the significance of the energy level diagram for a hydrogen atom?
It shows the allowed energy states and the energy required for transitions between them.
What governs the interactions of atoms and molecules?
The interaction of each atom or molecule with its neighbors.
What is observed in the spectrum of light emitted from rarefied gases?
A series of bright lines at discrete wavelengths.
Who showed that the equations hold for elliptical orbits as well?
German physicist Arnold Sommerfeld.
How much larger is the size of an atom compared to its nucleus?
About 10,000 to 100,000 times larger.
What principle is used to determine the distance of closest approach in the Geiger-Marsden experiment?
The conservation of total mechanical energy of the system.
What does the quantization of angular momentum refer to in the Bohr model?
Electrons moving in definite orbits have quantized angular momentum.
How does Thomson's model describe the atom?
As a spherical cloud of positive charges with electrons embedded in it.
What happens beyond the limit of the Balmer series?
Only a faint continuous spectrum is seen.
What does a negative total energy (E) imply about the electron in a hydrogen atom?
It implies that the electron is bound to the nucleus.
What is the Rydberg constant value?
1.097 × 10^7 m⁻¹.
What is the atomic number of gold?
What does the line spectrum of an atom consist of?
A set of isolated parallel lines termed as line spectrum, providing information about atomic structure.
What does the wave function obtained from the Schrödinger equation provide?
Information about the probability of finding an electron in various regions around the nucleus.
How is atomic energy often expressed?
In electron volts (eV).
What are the three postulates of Bohr's model for hydrogenic atoms?
(a) Electrons revolve in stable orbits without emitting energy. (b) Angular momentum is an integral multiple of h/2π. (c) Electrons can transition between orbits, emitting or absorbing photons.
How does the impact parameter affect the trajectory of an α-particle?
A small impact parameter results in large scattering, while a large impact parameter leads to nearly undeviated paths.
What does the small fraction of α-particles that rebound back indicate about the atom?
It indicates that the mass of the atom is concentrated in a small volume.
What is the formula for the quantized angular momentum of an electron in Bohr's model?
L = nh/2π.
What is the ionization energy required to free an electron from the ground state of a hydrogen atom?
13.6 eV.
What is the initial frequency of light emitted by an electron revolving around a proton in a hydrogen atom?
6.6 × 10^15 Hz.
What condition leads to the formation of standing waves in a string?
The total distance travelled by a wave must be an integral number of wavelengths.
What is the estimated size of the nucleus according to Rutherford's model?
About 10^-15 m to 10^-14 m.
What is the distance of closest approach to the nucleus of a 7.7 MeV α-particle?
3.0 × 10⁻¹⁴ m (30 fm).
What revolutionary idea did Bohr introduce regarding electron orbits?
Definite energy orbits for electrons.
What does Eq. (12.14) depict about orbital speed?
The orbital speed in the n-th orbit falls by a factor of n.
What significant achievement did Bohr accomplish regarding the hydrogen atom spectrum?
He provided an explanation that greatly stimulated progress towards modern quantum theory.
What is the initial mechanical energy of the α-particle before interaction?
The kinetic energy K of the incoming α-particle.
What did subsequent studies reveal about Thomson's model?
The distribution of electrons and positive charges is very different from that proposed in the Plum Pudding Model.
What does the final energy of the α-particle represent when it momentarily stops?
The electric potential energy U of the system.
What are the names of the other series of spectra for hydrogen?
Lyman, Paschen, Brackett, and Pfund series.
How do the radii of the orbits change with respect to n?
The radii of the orbits increase as n².
What is the empirical formula for the observed wavelengths in the Balmer series?
1/λ = R(1/n² - 1/2²).
What does the Bohr model correctly predict?
The gross features of hydrogenic atoms, particularly the frequencies of emitted or absorbed radiation.
What is the significance of the Lyman, Balmer, and Paschen series?
They represent different series of line spectra emitted by atomic hydrogen.
Who explained the puzzling nature of Bohr's second postulate in 1923?
Louis de Broglie.
What is the significance of the example involving a satellite in the context of Bohr's angular momentum postulate?
It applies Bohr's angular momentum postulate to a macroscopic object, suggesting a quantum number for the satellite's orbit.
How is the frequency of an emitted photon related to energy levels?
The frequency (ν) is given by hν = Ei - Ef, where Ei and Ef are the initial and final energy states.
In the analogy of the Rutherford model, how does the size of the electron's orbit compare to the nucleus?
The radius of the electron's orbit is 10^5 times larger than the radius of the nucleus.
What is the significance of the quantization condition in Bohr's model?
It determines the allowed values of angular momentum for electrons in orbits.
What happens to a hydrogen atom when it receives sufficient energy?
It may raise the electron to higher energy states, becoming an excited state.
What does the de Broglie hypothesis explain in relation to Bohr's model?
It provides an explanation for the quantization of angular momentum of the orbiting electron.
What is the main feature of Rutherford's model of the atom?
Most of the mass and all positive charge are concentrated in a tiny nucleus, with electrons revolving around it.
What is the Rydberg formula used for?
To calculate the wavelengths of spectral lines in the hydrogen spectrum.
What is the relationship between the number of atoms and intensity in ordinary light sources versus laser sources?
In ordinary sources, intensity is proportional to NI; in laser sources, it is proportional to N²I.
What did Rutherford discover through his experiments with alpha-rays?
The atomic nucleus.
What does Bohr's second postulate state about the angular momentum of an electron?
It is quantized, given by L = nh/2π.
What is the velocity of the revolving electron in a hydrogen atom?
Approximately 2.2 × 10^6 m/s.
What does the impact parameter 'b' represent in the context of α-particle collisions?
The perpendicular distance of the initial velocity vector of the α-particle from the center of the nucleus.
What is the relationship between electrostatic force and centripetal force in a stable orbit?
F_e = F_c.
What force holds the planetary system together, and how does it differ from the nucleus-electron system?
The planetary system is held by gravitational force, while the nucleus-electron system interacts by Coulomb’s Law of force.
If the dimensions of the solar system were scaled to the proportions of an atom, how would the Earth's distance from the Sun change?
The Earth would be much farther away from the Sun than it actually is.
How is the radius of the electron orbit calculated in Bohr's model?
Using the quantization condition of angular momentum.
What percentage of α-particles scatter by more than 1º?
About 0.14%.
What is the energy of the first excited state (n=2) of a hydrogen atom?
-3.40 eV.
What device was used to observe the scattered α-particles?
A rotatable detector consisting of a zinc sulphide screen and a microscope.
What did Rutherford argue was necessary to deflect an α-particle backwards?
A large repulsive force.
What occurs when an electron falls back to a lower energy state?
It emits a photon.
What phenomenon occurs when α-particles strike the zinc sulphide screen?
They produce brief light flashes or scintillations.
How much energy is required to excite a hydrogen atom from n=1 to n=2?
10.2 eV.
