CHEM 105A Week 2

What is the maximum number of electrons that can reside in an atomic orbital?

2

What amount of energy is required to move an electron from n=1 to n=∞? (Note: This is the energy required to completely remove an electron from the hydrogen atom).

2.178*10^-18 J

What is the de Broglie wavelength of an electron traveling at 3 m/s (mass of electron = 9.12*10^-31 kg)?

2.42*10^-4 m

What is the de Broglie wavelength of an 80 kg student running across campus at 3 m/s?

2.76*10^-36 m

A particular energy level in the hydrogen atom has E = -2.42 x 10-19 J. Use Bohr's model of the energy levels in hydrogen to calculate n for this level. Recall that atomic number (Z) of hydrogen is 1.

3

Which of the following is not true of Bohr's model of the atom? A. It can describe the emission spectra of multi-electron atoms B. It accurately describes the emission spectrum of H C. It assumes electrons are particles orbiting the nucleus on a deterministic path D. It postulated quantized energy levels for the electron

A. It can describe the emission spectra of multi-electron atoms

Bohr proposed a model of the hydrogen atom that describes electrons as... (Choose all that apply) A. Particles that move in circular orbits B. Particles that are attracted to the nucleus C. Particles that have only certain allowed orbits D. Particles in constant motion E. Particles that can be any arbitrary distance from the nucleus F. Particles that have wave-like behavior

A. Particles that move in circular orbits B. Particles that are attracted to the nucleus C. Particles that have only certain allowed orbits D. Particles in constant motion

In Bohr's atomic theory, when an electron moves from one energy level to another energy level more distant from the nucleus, A. Light is emitted B. Energy is emitted C. Energy is absorbed D. An electron is absorbed

C. Energy is absorbed

Consider an electron, which has a mass of 9.1 x 10 -31 kg. As the velocity of the electron increases, how does its de Broglie wavelength respond?

Decreases

The atomic orbitals developed using quantum mechanics...

Describe regions of space in which one is most likely to find an electron

The absorption and emission spectra of an atom are different than the absorption and emission spectra of its ions. This is evidence that spectra we observe are related to the number of which subatomic particles in the absorbing or emitting species?

Electrons

When electrons are passed through a crystal, they form a pattern on the other side that is very similar to a wave-interference pattern. What can we conclude from this result?

Electrons exhibit wave-like behavior

T or F: The emission spectrum of an atomic system is quantized (emission at only certain wavelengths is observed), but its absorption spectrum is continuous (system can absorb at all wavelengths).

F. Absorptive transitions are quantized also. The photon energy must match a possible transition exactly or nothing will happen...the electron will remain in the initial state.

T or F: The electron path is indicated by the surface of the orbital.

F. By convention, the surface of an orbital represents a volume in which there is a 90% chance of finding an electron, not a path for the electron.

T or F: Only electromagnetic radiation exhibits wave-particle duality.

F. Matter also exhibits wave-particle duality.

T or F: The radial and angular dependence of a given type of orbital changes as n increases.

F. Shape of orbital stays same at higher n; more nodes.

T or F: The hydrogen atom does not exhibit a 3s orbital.

F. The H atom can exhibit a 3s orbital if the electron is excited to the 3s state.

T or F: The energies available to the electron in any environment are quantized.

F. The energies available to the electron are quantized only when the electron is subject to a constraining potential (such as a nucleus).

The existence of spin quantum number ms

Indicates that the electron has intrinsic angular momentum

What is a fundamental problem with Bohr's model that caused it to be retired?

It assumes electrons are particles orbiting the nucleus on a deterministic path

T or F: The Bohr model of the atom was retired in part because it implied that the behavior of an electron could be completely described by treating it as a particle.

T

The size of the atomic orbital is associated with quantum number

n

One of the lines in the hydrogen atom spectrum has a wavelength of 486.1 nm. If this electron ends in the n=2 energy level, what energy level did it start in?

n=4