Based on the known sizes of subatomic particles, however, the surfaces of charged particles would have to be moving faster than the speed of light in order to produce the measured magnetic moments.
Furthermore, spin is quantized, meaning that only certain discrete spins are allowed. This situation creates all sorts of complications that make spin one of the more challenging aspects of quantum mechanics. Spin is likewise an essential consideration in all interactions among subatomic particles, whether in high-energy particle beams, low-temperature fluids or the tenuous flow of particles from the sun known as the solar wind.
Indeed, many if not most physical processes, ranging from the smallest nuclear scales to the largest astrophysical distances, depend greatly on interactions of subatomic particles and the spins of those particles. Stenger, professor of physics at the University of Hawaii at Manoa, offers another, more technical perspective: "Spin is the total angular momentum, or intrinsic angular momentum, of a body.
The spins of elementary particles are analogous to the spins of macroscopic bodies. In fact, the spin of a planet is the sum of the spins and the orbital angular momenta of all its elementary particles.
So are the spins of other composite objects such as atoms, atomic nuclei and protons which are made of quarks. In quantum mechanics, angular momenta are discrete, quantized in units of Planck's constant divided by 4 pi. Niels Bohr proposed that angular momentum is quantized in and used this to explain the line spectrum of hydrogen. These particles are all imagined as pointlike, so you might wonder how they can have spins. A simple answer might be, perhaps they are composite, too.
But deep theoretical reasons having to do with the rotational symmetry of nature lead to the existence of spins for elementary objects and to their quantization. Of particular significance is the difference between fermions, particles that, like the electron, have half-integer spins half-integer multiples of Planck's constant divided by 2 pi , and bosons, particles that have integer spins. Fermions obey the Pauli exclusion principle, which states that two identical fermions cannot exist in the same state; without the Pauli exclusion principle, chemistry would have no Periodic Table.
Identifying Spin Direction Determine the number of electrons the atom has. Draw the electron configuration for the atom. See Electronic Configurations for more information. Distribute the electrons, using up and down arrows to represent the electron spin direction. Example 2 Given 5f, identify all the possibilities of the four quantum numbers. Electron Spin: Where to begin? First, draw a table labeled n, L, m L and m s , as shown below: n L m L m s Then, depending on what the question is asking for, fill in the boxes accordingly.
So, there is zero electrons. References Petrucci, Ralph. Harwood, William. Herring, Geoffrey. Madura, Jeffery. Pearson Education, Inc. New Jersey, Li, Gengyun. What is the Electron Spin? Spin Publishing, Motz, Lloyd and Weaver, Jefferson H. Perseus, Practice Problems Identify the spin direction e.
Identify the spin direction of the outermost electron in a Chlorine Cl atom. The resulting two bands of the Stern-Gerlach experiment provide startling support for the ideas of quantum mechanics. Check Your Understanding If the Stern-Gerlach experiment yielded four distinct bands instead of two, what might be concluded about the spin quantum number of the charged particle?
According to nuclear theory, this moment is due to the orbital motion of quarks within the proton. The hyperfine structure of the hydrogen spectrum is explained by the interaction between the magnetic moment of the proton and the magnetic moment of the electron, an interaction known as spin-spin coupling.
The energy of the electron-proton system is different depending on whether or not the moments are aligned. Transitions between these states spin-flip transitions result in the emission of a photon with a wavelength of in the radio range.
Astronomers exploit this spectral line to map the spiral arms of galaxies, which are composed mostly of hydrogen Figure. A complete specification of the state of an electron in a hydrogen atom requires five quantum numbers: n , l , m , s , and. The names, symbols, and allowed values of these quantum numbers are summarized in Figure.
Note that the intrinsic quantum numbers introduced in this section s and m s are valid for many particles, not just electrons. For example, quarks within an atomic nucleus are also spin-half particles. As we will see later, quantum numbers help to classify subatomic particles and enter into scientific models that attempt to explain how the universe works.
Explain how a hydrogen atom in the ground state can interact magnetically with an external magnetic field. Even in the ground state , a hydrogen atom has magnetic properties due the intrinsic internal electron spin. The magnetic moment of an electron is proportional to its spin. Compare orbital angular momentum with spin angular momentum of an electron in the hydrogen atom.
List all the possible values of s and for an electron. Are there particles for which these values are different? For all electrons, and As we will see, not all particles have the same spin quantum number.
For example, a photon as a spin 1 , and a Higgs boson has spin 0. Are the angular momentum vectors and necessarily aligned?
An electron has a magnetic moment associated with its intrinsic internal spin. Spin-orbit coupling occurs when this interacts with the magnetic field produced by the orbital angular momentum of the electron. What is the magnitude of the spin momentum of an electron? Express you answer in terms of. What are the possible polar orientations of the spin momentum vector for an electron? Spin up relative to positive z -axis : Spin down relative to positive z -axis :.
For write all the possible sets of quantum numbers n , l , m ,. A hydrogen atom is placed in an external uniform magnetic field.
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