Atomic Theory Flashcards
How are isotopes distinguished and why?
Isotopes react the same way chemically and thus can be distinguished only by mass separation techniques (such as mass spectroscopy)
Explain the Thomson Experiment
The Thomson experiment demonstrated the existence of opposite charges in an atom and that charge is a fixed quantity. Thomson deflected a stream of charged particles (electrons) using an external electric field (the plates of a capacitor). Because the stream of particles bent in a uniform fashion, Thomson concluded that there was a consistent charge-to-mass ratio for the particles.
What is the mass spectrometer used for in general chemistry?
Charge-to-mass ratio and Isotopic abundance. Recall that isotopes are the same element w/ a different number of neutrons. By sending a charged particle into a perpendicular magnetic field, and observing the degree to which it curves, the isotopes with more neutrons will have a greater radius.
What is the 12C isotope?
The most abundant isotope of carbon.
What is the 13C isotope used for?
It is used in carbon NMR.
What is the 14C isotope used for?
It is used in carbon dating, because it undergoes decay.
What is the 1H isotope?
The most abundant isotope of hydrogen.
What is the 2H isotope used for?
Deuterium is used in proton NMR solvents.
What is the 3H isotope used for?
Tritium is used in radio-labeling experiments.
What is the 235U isotope used for?
It is used in nuclear fission.
What is the 238U isotope?
It is the most abundant isotope of uranium.
Explain the Millikan Oil Drop Experiment.
Its aim is to suspend a charged oil drop in an electric field to find the charge of an electron. If the particle is suspended (or falling at a constant velocity), then the net force is zero, so mg = -qE. Because we know g and we can set the electric field strength (thus we know E), by plugging in the average mass of an oil drop, we can solve for q, the charge of the electron.
What experiments address “what the are” questions about subatomic particles?
The Thomson experiment, the Millikan oil drop experiment, and the use of the mass spectrometer.
What experiment addresses “where they are” questions about subatomic particles?
The Rutherford experiment.
Explain the Rutherford Experiment.
It determined that atoms have dense nuclei with nearly all of the atomic mass centrally concentrated, and that metals have uniformly spaced atoms in the microscopic composition. An incident beam is focused ant a thin slice of gold. Because the incident beam mostly passes straight through the sample, with deflection being observed in only a few cases, it is concluded that the atom is made up predominantly of empty space. The mass occupies very little space and is not spread uniformly.
What equation describes the energy of a photon?
E = hv = (hc)/λ
What does “spin up” imply about the electron?
The spin produces a magnetic field vector oriented upward.
Describe paramagnetic and diamagnetic.
Paramagnetic–unpaired electrons.
Diamagnetic–paired electrons.
Pauli’s exclusion principle.
No two electrons can have the same set of quantum numbers.