University Physics Volume 3

# Summary

### 8.1The Hydrogen Atom

• A hydrogen atom can be described in terms of its wave function, probability density, total energy, and orbital angular momentum.
• The state of an electron in a hydrogen atom is specified by its quantum numbers (n, l, m).
• In contrast to the Bohr model of the atom, the Schrödinger model makes predictions based on probability statements.
• The quantum numbers of a hydrogen atom can be used to calculate important information about the atom.

### 8.2Orbital Magnetic Dipole Moment of the Electron

• A hydrogen atom has magnetic properties because the motion of the electron acts as a current loop.
• The energy levels of a hydrogen atom associated with orbital angular momentum are split by an external magnetic field because the orbital angular magnetic moment interacts with the field.
• The quantum numbers of an electron in a hydrogen atom can be used to calculate the magnitude and direction of the orbital magnetic dipole moment of the atom.

### 8.3Electron Spin

• The state of an electron in a hydrogen atom can be expressed in terms of five quantum numbers.
• The spin angular momentum quantum of an electron is = $+½+½$. The spin angular momentum projection quantum number is ms $=+½or−½=+½or−½$ (spin up or spin down).
• The fine and hyperfine structures of the hydrogen spectrum are explained by magnetic interactions within the atom.

### 8.4The Exclusion Principle and the Periodic Table

• Pauli’s exclusion principle states that no two electrons in an atom can have all the same quantum numbers.
• The structure of the periodic table of elements can be explained in terms of the total energy, orbital angular momentum, and spin of electrons in an atom.
• The state of an atom can be expressed by its electron configuration, which describes the shells and subshells that are filled in the atom.

### 8.5Atomic Spectra and X-rays

• Radiation is absorbed and emitted by atomic energy-level transitions.
• Quantum numbers can be used to estimate the energy, frequency, and wavelength of photons produced by atomic transitions.
• Atomic fluorescence occurs when an electron in an atom is excited several steps above the ground state by the absorption of a high-energy ultraviolet (UV) photon.
• X-ray photons are produced when a vacancy in an inner shell of an atom is filled by an electron from the outer shell of the atom.
• The frequency of X-ray radiation is related to the atomic number Z of an atom.

### 8.6Lasers

• Laser light is coherent (monochromatic and “phase linked”) light.
• Laser light is produced by population inversion and subsequent de-excitation of electrons in a material (solid, liquid, or gas).
• CD and Blu-Ray players uses lasers to read digital information stored on discs.
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