Advertisements
Advertisements
Question
A set of atoms in an excited state decays ______.
Options
in general to any of the states with lower energy.
into a lower state only when excited by an external electric field.
all together simultaneously into a lower state.
to emit photons only when they collide.
Advertisements
Solution
A set of atoms in an excited state decays in general to any of the states with lower energy.
Explanation:
When a hydrogen atom is excited, it returns to its: normal unexcited (or ground’ state) state by emitting the energy it had absorbed carli¢r, This energy is given out by the atom in the form of radiations of different wavelengths as the electron jumps down from a higher to a lower orbit. The transition from different orbits causes different wavelengths, these constitute spectral. series which ‘are characteristic of the atom emitting them. When observed through a spectroscope, these radiations are imaged as sharp and straight vertical lines of a single colour.
The spectral lines arising from the transition of an electron form a spectra series.
1. Mainly there are five series and each series is named after its discoverer as Lyman series, Balmer series, Paschen series, Bracket series and Pfund series.
2. According to Bohr's theory, the wavelength of the radiations emitted from hydrogen atom is given by
`1/λ = R[1/n_1^2 - 1/n_2^2]`
⇒ λ = `(n_1^2n_2^2)/((n_2^2 - n_1^2)R) = n_1^2/((1 - n_1^2/n_2^2)R)`
where n2 = outer orbit (electron jumps from this orbit), , = inner orbit (electron fills in this orbit)
A set of atoms in an excited state decays in general to any of the states with lower energy.
APPEARS IN
RELATED QUESTIONS
Find the frequency of revolution of an electron in Bohr’s 2nd orbit; if the radius and speed of electron in that orbit is 2.14 × 10-10 m and 1.09 × 106 m/s respectively. [π= 3.142]
How many electrons in an atom may have the following quantum numbers?
n = 4, `m_s = -1/2`
In Bohr’s model of the hydrogen atom, the radius of the first orbit of an electron is r0 . Then, the radius of the third orbit is:
a) `r_0/9`
b) `r_0`
c) `3r_0`
d) `9r_0`
The numerical value of ionization energy in eV equals the ionization potential in volts. Does the equality hold if these quantities are measured in some other units?
In a laser tube, all the photons
Find the wavelength of the radiation emitted by hydrogen in the transitions (a) n = 3 to n= 2, (b) n = 5 to n = 4 and (c) n = 10 to n = 9.
When a photon is emitted by a hydrogen atom, the photon carries a momentum with it. (a) Calculate the momentum carries by the photon when a hydrogen atom emits light of wavelength 656.3 nm. (b) With what speed does the atom recoil during this transition? Take the mass of the hydrogen atom = 1.67 × 10−27 kg. (c) Find the kinetic energy of recoil of the atom.
Calculate angular momentum of an electron in the third Bohr orbit of a hydrogen atom.
Draw energy level diagram for a hydrogen atom, showing the first four energy levels corresponding to n=1, 2, 3 and 4. Show transitions responsible for:
(i) Absorption spectrum of Lyman series.
(ii) The emission spectrum of the Balmer series.
When the electron orbiting in hydrogen atom in its ground state moves to the third excited state, show how the de Broglie wavelength associated with it would be affected.
The spectral line obtained when an electron jumps from n = 5 to n = 2 level in hydrogen atom belongs to the ____________ series.
In form of Rydberg's constant R, the wave no of this first Ballmer line is
Use Bohr's postulate to prove that the radius of nth orbit in a hydrogen atom is proportional to n2.
The first ionization energy of H is 21.79 × 10-19 J. The second ionization energy of He atom is ______ × 10-19J.
The line at 434 nm in the Balmer series of the hydrogen spectrum corresponds to a transition of an electron from the nth to second Bohr orbit. The value of n is ______.
In Bohr's theory of hydrogen atom, the electron jumps from higher orbit n to lower orbit p. The wavelength will be minimum for the transition ______.
Calculate the energy associated with third orbit of He+.
The radius of hydrogen atom in the ground state is 0.53 Å. The radius of Li2+ ion (atomic number = 3) in a similar state is ______.
Which principle did Bohr propose?
What happens when an electron makes the transition described by Bohr’s third postulate?
