Structure of the Atom Flashcards
What are the two Bohr’s postulates for the atom?
- Allowed or the permissible orbits for which the angular momentum of the electron is the integral multiple of reduced Planck’s constant. These are called stationary orbits.
- An atoms radiates energy only when an electron jumps from a stationary orbit of higher energy to one of lower energy. The energy of the radiation is the difference in energies of the electron at two orbits.
Derive the expression of Bohr’s stationary orbits’ radius and total energy of the electrons at that orbit.
Refer to the book for the answer.
What are the considerations or the assumptions made to calculate Bohr’s orbit?
Charge of nucleus and electron.
Mass of nucleus and electron.
Mass of nucleus is far more than the mass of electron.
And, the radius of the orbit.
Write the formula for Bohr’s radius and the Total energy of the nth Bohr’s orbit?
Refer to the book
What was the Bohr’s interpretation of the Hydrogen spectrum?
Refer to the book
What is Rydberg constant? Write its formula and where it came from? Also write its value in units.
Refer to the book for this
Explain the spectral series of the hydrogen atom?
Refer to the book
Write the value of total energy of the electron for the first four Bohr’s orbits?
for 1, -13.6 eV
for 2, -3.4 eV
for 3, - 1.51eV
for 4, -0.85 eV
What is one electron volt? What is it’s value?
the energy gained by an electron when it has been accelerated by a potential difference of 1 volt.
The value = 1.602176634×10^(−19) J.
= charge of the electron * 1 volt
Difference between the ionization potential and the excitation potential with an illustrative example.
Refer to the book
Draw a well labelled schematic diagram of Frank and Hertz experiment and the graph obtained. Explain both.
Refer to the book
What is the result of Frank and Hertz experiment?
This experiment shows in a very convincing way the existence of the discrete energy levels in atom.
What does Frank and Hertz experiment show?
The energy lost by the electron in its inelastic collision with the mercury atoms reappears as a quantum of energy of the wavelength hc/E.
How the collision is inelastic in Frank and Hertz experiment?
What is the main drawback of Frank and Hertz experiments?
It cannot distinguish between excitation potential and ionization potential.
How though?
Explain the role of three different voltages in Frank and Hertz experiment.
Refer to the book for the answer.
Explain the graph of the Frank and Hertz experiment.
Refer to the book
Write the four basic formula used in Sommerfeld’s Relativistic Atom Model.
Refer to the notes
Write the two assumptions of the Sommerfeld’s Relativistic Atom Model.
- The path of an electron orbiting around a nucleus is, in general, ellipse. The circular orbits are a special case of this.
2.The mass of the electron orbiting around the nucleus varies relativistically with its velocity.
Write the equation of an ellipse in polar coordinates.
Refer to the book
Write the standard integral and its integrated value, that is involved in mathematic analysis of Sommerfeld’s Relativistic Atom Model.
Refer to the book.
What are the allowed orbits in Sommerfeld’s Relativistic Atom Model? Explain something about these orbits.
Refer to the book. The allowed orbits are those for which the ratio of major and minor axes is that of two integers.
Explain how, for a given value of n, n(phi) can assume only n different values, which means there can be only n elliptical orbits of different eccentricities.
Refer to the book for explanation.
Explain the fine structure of H(alpha) line using Sommerfeld’s Relativistic Atom Model.
Refer to the book for explanation.
Obtain the expression for the total energy of the Sommerfeld’s Relativistic Atom and compare it with that of Bohr’s. Also explain what does it mean.
Refer to the book.
Explain the relativistic variation of mass and its consequences in Sommerfeld’s Relativistic Atom Model.
Refer to the book
What is the fine structure constant and what is its significance?
Refer to the book.
What were the drawbacks of Sommerfeld’s Relativistic Atom Model.
-couldn’t predict the correct numbers of fine structures of spectral lines of hydrogen.
- couldn’t explain the complex spectra of alkali metals like sodium
-Zeeman and Stark effect
What were the main drawbacks of Bohr’s theory?
multiple structures of spectral lines in the simple hydrogen atom.
Zeeman and Stark effect
it couldn’t explain how the orbital electrons in an atom were distributed around the nucleus.
Explain spatial and spin quantization according to the vector atom model.
Refer to the book.
What are quantized vectors? Why are they called so?
Refer to the book
Explain the quantum numbers associated with the vectors atom model.
Refer to the book.
Explain the applications of Pauli Exclusion Principle.
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Derive the expression for the magnetic dipole moment due to the Orbital Motion of the Electron, and Spin motion of the electron.
Refer to the book for help.
How are magnetic dipole moment for orbital motion and spin motion of the electron, in an external magnetic field calculated?
It is calculated for the orbital motion since the geometry is known. But for the spin motion, it is not calculated, but simply assumed, as nothing is known about the shape and charge distribution of an electron.
What is gyromagnetic ratio?
ratio of magnetic dipole moment to the angular momentum
For which results, the Stern and Gerlach Experiment’s provide evidence for?
It provides the direct evidence for the magnetic moments of an atom due to the orbital and spin motion of the electrons, and the space quantization of those magnetic moments.
Sketch the diagram and explain the construction, theory and experimental results of Frank and Hertz experiment.
…
What was the magnetic moment of the silver atoms used in Frank and Hertz experiments?
One Bohr Magneton in the direction of the field..
How though?
What about the orbital angular momentum in Frank and Hertz experiment?
Fill out the answer
What is the selection rule in case of the Sommerfeld atomic model?
the change in n phi should always be unity
Write about the Larmor’s Theorem.
Look at the book
What is the formula of Larmor’s angular frequency?
RTB
Derive the expression for the change in KE due to the Larmor’s precession.
rtb
Even though nine transitions are possible, why only three lines are seen in normal Zeeman effect?
rtb
What is normal and anomalous Zeeman effect?
When the splitting occurs into two or three lines, the Zeeman effect is called Normal Zeeman effect, and when the splitting occurs into more than three lines, it is referred as anomalous Zeeman effect.
Why the direction of total magnetic moment is not in alignment with the total momentum vector? Is it related to the supposition of magnetic moment due to spin motion of the electron?
fill out the answer
