Atomic Theories and Models Quiz

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Questions and Answers

What determines the stationary orbits in which an electron can revolve?

The angular momentum being an integer multiple of (h / 2π) (correct)

The mass of the nucleus

The velocity of the electron

The charge of the nucleus

How is the radius of an electron's orbit related to the principal quantum number?

It is directly proportional to the principal quantum number.

It is equal to the principal quantum number.

It is inversely proportional to the square of the principal quantum number.

It is proportional to the square of the principal quantum number. (correct)

Which of the following statements about the energy of emitted photons is correct?

Photon energy is independent of the electron's orbits.

Energy is the difference between the energies of the two orbits. (correct)

Photon energy is only emitted when an electron is at rest.

Photon energy increases with the number of electron jumps.

What is the total energy of an electron in orbit n in terms of its atomic number Z?

E = – 13.6 Z² / n² eV Signup and view all the answers

Which series in the hydrogen spectrum corresponds to transitions from higher orbits to n = 1?

Lyman Series Signup and view all the answers

What is the relationship between the frequency of an electron's orbit and its quantum number n?

Frequency is proportional to Z/n. Signup and view all the answers

What is the potential energy of an electron in orbit n in terms of atomic number Z?

Ep = – 27.2 Z² / n² eV Signup and view all the answers

Which of the following best describes the concept of quantized energy levels?

Energies are discrete and defined by specific quantum numbers. Signup and view all the answers

What is described as the tiny region at the center of the atom where positive charge and mass are concentrated?

Nucleus Signup and view all the answers

Which model of the atom incorrectly posited that electrons are distributed uniformly throughout a positively charged sphere?

Thomson's Atomic Model Signup and view all the answers

What key concept did Rutherford's scattering experiments reveal about the nucleus?

Its radius is approximately 10^-15 m. Signup and view all the answers

According to the limitations of Rutherford's Atomic Model, what happens to electrons as they orbit the nucleus?

They emit energy as electromagnetic waves. Signup and view all the answers

What does the impact parameter represent in relation to Rutherford's experiments?

The perpendicular distance from the velocity vector to the center of the nucleus Signup and view all the answers

Which of the following equations correctly represents the distance of closest approach for an α-particle?

$r_0 = \frac{1}{4\pi \epsilon_o} \frac{Ze^2}{E_k}$ Signup and view all the answers

What fundamental reason led to the rejection of Thomson's Atomic Model?

It failed to describe the behavior of electrons in spectral emissions. Signup and view all the answers

In Rutherford's model of the atom, how is the total charge of the nucleus balanced?

By an equal number of electrons Signup and view all the answers

Study Notes

Dalton's Atomic Theory

States that elements are composed of atoms, which are indivisible particles.
Atoms of the same element are identical, while atoms of different elements have different properties.
This theory served as a foundational concept for modern atomic theory.

Thomson's Atomic Model

Described the atom as a positively charged sphere with negatively charged electrons embedded within it.
The model was based on the idea that the atom is electrically neutral.
This model was unable to explain certain observed phenomena, including the spectral series of hydrogen and the scattering of alpha particles.

Rutherford's Atomic Model

Proposed based on experiments involving the scattering of alpha particles by thin gold foil.
The model described the atom as consisting of a small, dense, positively charged nucleus at the center, with negatively charged electrons orbiting around it.
The model explained the observed large-angle scattering of alpha particles.

Distance of Closest Approach

This refers to the minimum distance an alpha particle comes to the nucleus before being deflected.
The value depends on the alpha particle's kinetic energy and the nucleus's atomic number.

Impact Parameter

The perpendicular distance between an alpha particle's velocity vector and the nucleus when the particle is far away.
Determines the scattering angle of the alpha particle.

Rutherford's Scattering Formula

Relates the number of alpha particles scattered at a specific angle to the impact parameter, atomic number, energy of the alpha particles, and thickness of the foil.

Limitations of Rutherford's Model

It failed to explain the stability of atoms, as the model predicted that electrons would lose energy and spiral into the nucleus.
It couldn't explain the line spectrum of elements.

Bohr's Atomic Model

Proposed that electrons can only exist in specific, quantized orbits around the nucleus.
The model introduced the idea of energy levels, where electrons can transition between orbits by absorbing or emitting photons of light.
The angular momentum of an electron in an orbit is quantized, meaning it can only take on specific values.

Hydrogen Spectrum Series

The hydrogen atom emits a unique set of spectral lines, which are characteristic of the element.
There are several spectral series, including the Lyman, Balmer, Paschen, Brackett, and Pfund series.
The series correspond to transitions of electrons between different energy levels.

Lyman Series

Occurs when electrons transition from higher energy levels (n = 2, 3, 4...) to the ground state (n = 1).
Emits ultraviolet radiation.

Balmer Series

Occurs when electrons transition from higher energy levels (n = 3, 4, 5...) to the second energy level (n = 2).
Emits visible light.

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Description

Test your knowledge on the key concepts of Dalton's Atomic Theory, Thomson's Atomic Model, and Rutherford's Atomic Model. This quiz covers the foundational ideas that shaped our understanding of atomic structure. Dive in to see how these theories interconnect and their significance in modern science!