Atomic Structure and Spectra Quiz
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Questions and Answers

What did Rutherford's nuclear model fail to explain?

  • Why atoms emit light of only discrete wavelengths (correct)
  • The composition of alpha particles
  • The mass of the nucleus
  • The stability of electrons

Which of the following components of the atom was being studied in the alpha-particle scattering experiment?

  • Neutrons
  • Alpha particles (correct)
  • Protons
  • Electrons

What was the purpose of the lead bricks in the experiment conducted by Geiger and Marsden?

  • To collimate the beam of alpha particles (correct)
  • To increase the energy of alpha particles
  • To absorb stray particles
  • To measure the thickness of the gold foil

What was used as a detector for the scattered alpha particles in the experiment?

<p>A zinc sulphide screen and microscope (A)</p> Signup and view all the answers

In which year did the experiment by Geiger and Marsden take place?

<p>1911 (D)</p> Signup and view all the answers

What phenomenon is observed when alpha particles strike the zinc sulphide screen?

<p>Production of scintillations (C)</p> Signup and view all the answers

What characteristic made Rutherford’s nuclear model groundbreaking?

<p>It replaced the plum pudding model (D)</p> Signup and view all the answers

What issue arises when considering electrons revolving around the nucleus in a classical model?

<p>Electrons would lose energy and spiral into the nucleus (B)</p> Signup and view all the answers

What is the orbital radius calculated for the electron in this example?

<p>5.3 × 10–11 m (C)</p> Signup and view all the answers

What is the velocity of the revolving electron as computed in the example?

<p>2.2 × 10^6 m/s (C)</p> Signup and view all the answers

How is an emission line spectrum characterized?

<p>Bright lines on a dark background (B)</p> Signup and view all the answers

What happens when white light passes through a gas?

<p>It results in an absorption spectrum (B)</p> Signup and view all the answers

What is described as a 'fingerprint' for identifying a gas?

<p>The emission line spectrum (D)</p> Signup and view all the answers

Which of the following best describes hydrogen's spectrum among elements?

<p>It exhibits the least complexity in its spectrum (B)</p> Signup and view all the answers

In an emission line spectrum, what is the nature of the background?

<p>Dark with bright lines (C)</p> Signup and view all the answers

What aspect of atomic spectra indicates a lack of order in spectral lines?

<p>Irregularity in the initial observed spectrum (C)</p> Signup and view all the answers

What does the negative sign of the total energy of an electron indicate?

<p>The electron is bound to the nucleus. (C)</p> Signup and view all the answers

How can the energy equations be rewritten to express energy in electron volts?

<p>By converting joules to electron volts using the relationship $1 eV = 1.6 × 10^–19 J$. (A)</p> Signup and view all the answers

What does the Bohr Model introduce about the orbits of electrons?

<p>Electrons move in definite energy orbits. (D)</p> Signup and view all the answers

What was the major assumption made in the derivation of the energy equations?

<p>Electrons move in circular orbits. (A)</p> Signup and view all the answers

Who showed that the equations continue to hold for elliptical orbits?

<p>Arnold Sommerfeld (C)</p> Signup and view all the answers

What does the quantization of angular momentum imply in the Bohr Model?

<p>Angular momentum is restricted to discrete values. (B)</p> Signup and view all the answers

In terms of energy, how does an electron escape from a hydrogen atom?

<p>It requires energy to overcome the binding energy. (A)</p> Signup and view all the answers

How has the understanding of atomic structure evolved since the Bohr Model?

<p>It has been refined through the development of quantum mechanics. (A)</p> Signup and view all the answers

Which series of the hydrogen spectrum was first observed by Johann Jakob Balmer?

<p>Balmer series (B)</p> Signup and view all the answers

What is the wavelength of the Hα line in the Balmer series?

<p>656.3 nm (D)</p> Signup and view all the answers

What value of n is used to find the wavelength of the Hα line in the Balmer formula?

<p>3 (B)</p> Signup and view all the answers

What is the Rydberg constant value used in the Balmer formula?

<p>1.097 × 10^7 m⁻¹ (C)</p> Signup and view all the answers

What happens to the lines in the Balmer series as the wavelength decreases?

<p>They appear closer together and weaker in intensity. (B)</p> Signup and view all the answers

What is the shortest wavelength observed in the Balmer series?

<p>364.6 nm (B)</p> Signup and view all the answers

Which of the following series corresponds to n = 4, 5, 6 for hydrogen?

<p>Paschen series (D)</p> Signup and view all the answers

Beyond the limit of the Balmer series, what type of spectrum is observed?

<p>Only a faint continuous spectrum (A)</p> Signup and view all the answers

What fundamental aspect does the electron-electron electric force interaction possess in multi-electron atoms compared to the gravitational forces in the solar system?

<p>The electric force is comparable in magnitude to other forces acting on electrons. (C)</p> Signup and view all the answers

Which of the following is a limitation of the Bohr model when applied to multi-electron atoms?

<p>It assumes planetary-like behavior of electrons. (B)</p> Signup and view all the answers

In quantum mechanics, how does the treatment of energy levels differ from the Bohr model?

<p>One energy level may correspond to multiple quantum states. (C)</p> Signup and view all the answers

What is the primary characteristic of the orbits in which an electron revolves in a hydrogen atom according to Bohr's model?

<p>Orbits are stationary and do not emit radiant energy. (C)</p> Signup and view all the answers

Which of the following accurately reflects a feature of the Bohr model concerning the frequency of electron revolution and spectral lines?

<p>The frequencies are linked through the difference of two orbital energies. (D)</p> Signup and view all the answers

Which series in atomic hydrogen spectrum corresponds to transitions where the final orbit has n=2?

<p>Lyman series (B)</p> Signup and view all the answers

What does Bohr's quantization condition state about angular momentum in hydrogen atoms?

<p>Angular momentum is an integral multiple of h/2π. (A)</p> Signup and view all the answers

Why is the Bohr model still considered useful despite its limitations?

<p>It serves well with classical mechanics concepts. (D)</p> Signup and view all the answers

When an electron transitions to a lower energy orbit, what is emitted?

<p>A photon with energy equal to the energy difference between the initial and final states. (C)</p> Signup and view all the answers

What aspect of the hydrogen atom's energy levels can be attributed solely to the principal quantum number n?

<p>The energy of the system. (D)</p> Signup and view all the answers

In what way does Bohr's semiclassical model primarily diverge from quantum mechanics?

<p>It provides a deterministic view of electron behavior. (B)</p> Signup and view all the answers

What is the frequency of an emitted photon when an electron jumps to a lower energy state?

<p>hν = Ei – Ef (A)</p> Signup and view all the answers

What unique aspect of the quantum states is necessary for understanding atomic structure in comparison to the Bohr model?

<p>Quantum states incorporate four quantum numbers. (B)</p> Signup and view all the answers

Which series of atomic hydrogen corresponds to transitions with initial states n=3 or above?

<p>Paschen series (C)</p> Signup and view all the answers

How is the energy of an absorbed photon related to an electron's transition within an atom?

<p>The energy is the same as the emitted photon’s energy. (B)</p> Signup and view all the answers

What determines the specific radii at which an electron orbits the nucleus in a hydrogen atom?

<p>The quantization condition of angular momentum. (C)</p> Signup and view all the answers

Flashcards

Rutherford's Nuclear Model

A model of the atom where a dense, positively charged nucleus is surrounded by negatively charged electrons. It was revolutionary for its time, but fell short of explaining the spectral emission of light by atoms.

Alpha-Particle Scattering Experiment

An experiment conducted by Geiger and Marsden, directed by Rutherford, where alpha particles were shot at a thin gold foil. The results provided evidence for the nuclear model of the atom.

Alpha Particles

Positively charged particles emitted by radioactive substances, such as bismuth-214. These particles are used in the Rutherford scattering experiment.

Gold Foil

The thin sheet of gold used in Rutherford's experiment. Alpha particles were shot at this foil to study how they interact with the atoms.

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Scattering

The deflection of alpha particles when they hit the gold foil. The amount of scattering depends on the interaction with the nucleus.

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Zinc Sulfide Screen

The detector used in Rutherford's experiment to observe the scattered alpha particles. The screen produces flashes of light when struck by an alpha particle.

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Discrete Wavelengths

Specific colors or wavelengths of light emitted by atoms. These are unique for each element and cannot be explained by Rutherford's model.

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Why Rutherford's Model Couldn't Explain Spectral Emission

Rutherford's model couldn't explain why atoms emit specific colors of light, as the electron's orbit would produce a continuous spectrum instead. This led to the development of new models like Bohr's model.

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Orbital radius

The distance between the nucleus and the electron in an atom.

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What is the formula for calculating orbital radius?

The formula for calculating orbital radius is: r = (e^2)/(2 * E) where e is the charge of the electron, and E is the energy of the electron.

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Atomic spectra

Unique patterns of light emitted or absorbed by an element, serving as a fingerprint for identification.

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Emission line spectrum

A spectrum with bright lines on a dark background, created by excited atoms releasing specific wavelengths of light.

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Absorption spectrum

Dark lines in a spectrum, corresponding to wavelengths absorbed by the material as white light passes through it.

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Spectral series

Regular patterns observed in the frequencies of light emitted by a particular element.

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What is the simplest atom?

Hydrogen is the simplest atom because it has only one proton and one electron.

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What is the key to understanding atomic spectra?

The key to understanding atomic spectra is the excitation of atoms, which causes them to emit or absorb specific wavelengths of light.

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Balmer Series

The series of visible spectral lines of hydrogen, discovered by Johann Jakob Balmer in 1885.

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Hα Line

The line with the longest wavelength in the Balmer series, at 656.3 nm, appearing red.

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Balmer Formula

An empirical formula that predicts the wavelengths of the lines in the Balmer series.

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Rydberg Constant

A fundamental constant in atomic physics, representing the energy difference between the ground and first excited state of hydrogen.

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Lyman, Paschen, Brackett, Pfund

Other spectral series of hydrogen, discovered after the Balmer series, named after their discoverers.

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Continuous Spectrum

A spectrum containing all wavelengths of light, without any distinct lines or gaps.

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Limit of a Spectral Series

The shortest wavelength in a spectral series, beyond which no distinct lines appear, only a continuous spectrum.

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What are spectral series?

Regular patterns observed in the frequencies of light emitted by a particular element.

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Lyman Series

A spectral series in hydrogen where electrons transition from higher energy levels to the ground state (n=1).

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Bohr's Postulate 1

Electrons can only exist in specific, stable orbits around the nucleus, called stationary orbits, without radiating energy.

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Bohr's Postulate 2

The angular momentum of an electron in a stationary orbit is quantized, meaning it can only take on certain values.

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Bohr's Postulate 3

An electron can jump between stationary orbits by absorbing or emitting a photon, the energy of which is equal to the energy difference between the orbits.

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What does the formula hν = Ei - Ef describe?

The relationship between the energy difference between two energy levels in an atom and the frequency of the photon emitted or absorbed during an electron transition.

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Quantum Number

An integer that describes the quantized values of an electron's energy, angular momentum, and spin, determining its specific state within an atom.

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Bohr Model

A model of the atom where electrons orbit the nucleus in specific energy levels, quantized according to Planck's constant. This model successfully explains the spectral lines of hydrogen.

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Energy Level

A specific, quantized energy state that an electron can occupy in an atom, described by the principal quantum number (n). Higher energy levels correspond to orbits farther from the nucleus.

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Quantized Energy

Energy is not continuous, but exists in discrete, fixed values. This applies to electron energy levels in an atom, explaining why atoms emit or absorb specific wavelengths of light.

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Electron Volt (eV)

A unit of energy commonly used in atomic physics, equal to the energy gained by an electron when it moves through a potential difference of one volt.

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Ground State

The lowest possible energy state an electron can occupy within an atom. Electrons are naturally found in this state unless excited.

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Excited State

An energy level higher than the ground state. Electrons can be excited by absorbing energy, moving to a higher energy level. They eventually decay back down to the ground state, releasing the absorbed energy.

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Spectral Lines

Bright or dark lines on a spectroscope, indicating specific wavelengths of light emitted or absorbed by an atom. Each element has a unique set of lines, like an atomic fingerprint.

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Atomic Emission Spectrum

The spectrum of light emitted by excited atoms as they transition to lower energy levels. This spectrum consists of bright lines, each corresponding to a specific wavelength of light.

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Why Bohr's Model Fails for Multi-Electron Atoms?

In multi-electron atoms, electron-electron interactions are significant, making the simple Bohr model inaccurate. This is because the forces between electrons are comparable to the electron-nucleus force, unlike in the solar system where planetary interactions are negligible compared to the Sun's gravitational pull.

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Bohr's Postulates: Quantum Numbers

Bohr introduced quantum numbers to describe electron orbits. These numbers quantize energy levels, meaning electrons can only exist at specific energy states. This is different from classical physics, where electrons could have any energy.

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Quantum Mechanics vs. Bohr's Model

Quantum mechanics, the more refined theory, supports Bohr's idea of quantized energy levels. However, it allows for multiple quantum states at a given energy level, unlike Bohr's single-state model.

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Electron Revolution Frequency

Bohr's model incorrectly assumed the electron's revolution frequency is the same as the frequency of the emitted spectral line. In reality, the emitted frequency is determined by the difference in energy levels divided by Planck's constant.

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Bohr's Model: Semiclassical

Bohr's model is a semi-classical approximation, combining elements of classical physics (like orbits) with quantum ideas (quantified energy levels). It's not a complete picture of atomic structure.

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Bohr Model: Why Still Useful?

Despite its limitations, Bohr's model remains valuable for understanding atomic spectra and basic concepts. Its simplicity and ability to explain key features of hydrogen spectra make it a useful teaching tool.

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Explain how Bohr's model was limited.

Bohr's model only works for hydrogen. Its limitations include the incorrect assumption about the frequency of electron revolution and the lack of explanation for multiple electron atoms.

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What is the importance of Bohr's model?

Bohr's model was a revolutionary step in understanding atomic structure. It introduced the concept of quantized energy levels and provided a foundation for later quantum theories.

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Study Notes

Atomic Structure

  • Atoms are electrically neutral, containing equal positive and negative charges
  • Thomson's model: Atom is a sphere of positive charge with electrons embedded
  • Rutherford's model: Atom has a small, dense, positively charged nucleus with electrons orbiting around it
  • Rutherford's nuclear model explains scattering of alpha particles by gold foil
  • Alpha particles are deflected significantly when they pass close to the densely-packed positive charge of the nucleus
  • This indicates that most of the atom's mass is concentrated in a tiny nucleus

Atomic Spectra

  • Elements emit and absorb light at specific wavelengths, creating unique spectral lines
  • Each element has a distinct line spectrum
  • Hydrogen's spectrum has characteristic series (Lyman, Balmer, Paschen)
  • Spectral lines represent electron transitions between energy levels within the atom
  • Quantum jumps; electrons move from one energy level (orbit) to another.
  • The frequency of the emitted or absorbed light is directly proportional to the energy difference between the orbits
  • Using the energy level diagram, we can determine the energy levels from observed wavelengths
  • Bohr model successfully predicted the hydrogen atom energy levels and spectral lines

Bohr Model

  • Bohr's postulates:
    • Electrons orbit the nucleus in fixed energy levels without emitting radiation
    • Electron orbits have quantized angular momentum (integral multiples of h/2π)
    • Electrons can transition between energy levels by absorbing or emitting photons of specific energy
  • Bohr model explains the stability of atoms
  • Bohr model successfully accounted for hydrogen's atomic spectrum
  • The Bohr model introduced the concept of quantized energy levels

De Broglie's Explanation of Bohr's Postulates

  • De Broglie’s hypothesis: Electrons exhibit wave-like properties
  • Standing waves: Electron orbits must have whole number of de Broglie wavelengths.
  • Quantization of angular momentum results from electron wave interference, forming a standing wave around the nucleus.

Frank-Hertz Experiment

  • Frank-Hertz experiment verified quantized energy levels in atoms
  • Observed discrete energy-loss values in electrons passing through a gas, consistent with transitions between energy levels

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Description

Test your knowledge on atomic structure and spectra with this quiz. Explore models of the atom, including Thomson's and Rutherford's theories, as well as the unique spectral lines produced by different elements. Understand the significance of electron transitions and energy levels in atomic physics.

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