The emergence of line spectra from a gas when a current passes through it was an
ID: 2102690 • Letter: T
Question
The emergence of line spectra from a gas when a current passes through it was an observed phenomenon waiting for an explanation in the early 20th century. The atomic line spectra coming from elements such as hydrogen had been analyzed since the late 19th century. By studying the wavelength of the emerging radiation of hydrogen, experimenters found (often by trial and error) that the wavelengths in those spectra were described by the formula
In 1913, Niels Bohr provided an explanation for the observations made in experiments by proposing that each electron in an atom had only certain allowable energy levels. Furthermore, he postulated that when an electron changed its energy level, it must emit or absorb a single photon with the energy equal to the energy difference between the two levels.
A) What is the change in energy delta E of the hydrogen atom as the electron makes the transition from the n=3 energy level to the n=1 energy level?
delta E=?eV
B) When an atom makes a transition from a higher energy level to a lower one, a photon is released. What is the wavelength of the photon that is emitted from the atom during the transition from n=3 to n=1?
Express your answer numerically in angstroms.
C)When the hydrogen atom makes the transition from the n=2 to the n=1 energy level, it emits a photon. This photon can be absorbed by to a singly ionized helium atom (He2+) in its second energy level (n-initial=2), causing it to move to a higher energy level. To what final energy level number nfinal can the photon promote the helium ion?
Note that He+ has two protons in its nucleus and a single electron.
Explanation / Answer
a) E = hc / lambda
and 1/lambda = R( 1/Nf^2 - 1/Ni^2)
up on solving for Nf=3 and Ni = 1
we get E= 12.04 eV
b
B) lambda = 1.03 *10^-7 m
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