Characteristics of Bohr's Atomic Model

Q. The size of an atom is of the order of

1. ${10}^{-8}m$
2. ${10}^{-10}m$
3. ${10}^{-12}m$
4. ${10}^{-14}m$

Q.

With the increase in the radius of the orbit, the energy of an electron _______.

Q. The ratio of the energies of the hydrogen atom in its first to second excited state is

1. $\frac{1}{4}$
2. $\frac{4}{9}$
3. $\frac{9}{4}$
4. $4$

Q. What is the momentum of photon of energy 3 MeV in $kgm{s}^{-1}$?

1. $9\times {10}^{-21}$
2. $1.6\times {10}^{-21}$
3. $3\times {10}^{-28}$
4. $9\times {10}^{-28}$

Q. If the kinetic energy of a free electron doubles, its de-Broglie wave length changes by the factor of

1. $\sqrt{2}$
2. $2$
3. $\frac{1}{2}$
4. $\frac{1}{\sqrt{2}}$

Q. Bohr's model is applicable only to one electron atoms like helium He⁺ and lithium Li⁺⁺ apart from hydrogen atom.

1. True
2. False

Q. The kinetic energy of the electron in an orbit of radius r in hydrogen atom is (e = electronic charge)

1. $\frac{e^2}{r^2}$
2. $\frac{e^2}{2r}$
3. $\frac{e^2}{r}$
4. $\frac{e^2}{2r^2}$

Q. The ratio of areas within the electron orbits for the first excited state to the ground state for hydrogen atom is

1. 16 : 1
2. 18 : 1
3. 4 : 1
4. 2 : 1

Q. The radius of the first orbit of hydrogen in $0.528\dot{A}$. The radius of second orbit of hydrogen is

1. $4.752\dot{A}$
2. $2.112\dot{A}$
3. $0.071\dot{A}$
4. $0.142\dot{A}$

Q. When an electron in hydrogen atom is excited, from its $4^{th}$ to $5^{th}$ stationary orbit, the change in angular momentum of electron is (Planck’s constant:$h=6.6\times {10}^{-34}J-s$)

1. $4.16\times {10}^{-34}J-s$
2. $3.32\times {10}^{-34}J-s$
3. $1.05\times {10}^{-34}J-s$
4. $2.08\times {10}^{-34}J-s$

Q.

Explain the energy changes involved in the formation of $F^{-}$ and $O^{2-}$ from their respective atoms.

Q. Consider the spectral line resulting from the transition n = 2 to n = 1 in the atoms and ions given below. The shortest wavelength is produced by

1. Hydrogen atom
2. Deuterium atom
3. Uni-ionized helium
4. di-ionized lithium

Q. Find the radius of ${\text{He}}^{+}$ ion in its second excited state.
$($Assume Bohr's model is applicable$)$

1. $2.4A^{\circ }$
2. $1.2A^{\circ }$
3. $4.2A^{\circ }$
4. $5.3A^{\circ }$

Q. If an orbital electron of the hydrogen atom jumps from the ground state to a higher energy state, its orbital speed reduces to half its initial value. If the radius of the electron orbit in the ground state is r, then the radius of the new orbit would be

1. 2r
2. 4r
3. 8r
4. 16r

Q. In Bohr’s model of hydrogen atom, the ratio between the period of revolution of an electron in orbit n = 1 to the period of the electron in the orbit n = 2 is

1. 1 : 2
2. 2 : 1
3. 1 : 4
4. 1 : 8

Q.

The azimuthal quantum number indicates the angular momentum of an electron.

1. True
2. False

Q. The ionization potential of an electron in the second orbit of $H{e}^{+}$ atom is

1. 13.6 eV
2. 27.2 eV
3. 54.4 eV
4. 100 eV

Q. Ionisation energy for hydrogen atom in the ground state is E. What is the ionisation energy of $L{i}^{++}$ atom in the $2^{nd}$ excited state

1. E
2. 3 E
3. 6 E
4. 9 E

Q. In a beryllium atom, if $a_0$be the radius of the first orbit, then the radius of the second orbit will be in general

1. $n{a}_0$
2. $a_0$
3. $n^2{a}_0$
4. $\frac{a_0}{n^2}$

Q. The ground state energy of hydrogen atom is -13.6eV. The kinetic energy of the electron in this state is:

1. 1.85 eV
2. 13.6 eV
3. 6.8 eV
4. 3.4 eV

Q. If an electron of an atom goes from $n=1$ to $n=3$ then its time period become _______ times of the initial value.

1. $25$
2. $1/25$
3. $27$
4. $1/27$

Q.

Energy of electron in a orbit of H-atom is

1. Positive

2. Negative

3. Zero

4. Nothing can be said

Q. In the Bohr model of the hydrogen atom, let $R$, $v$ and $E$ represent the radius of the orbit, the speed of electron and the total energy of the electron respectively. Which of the following quantity is directly proportional to the quantum number n

1. $\frac{R}{E}$
2. $\frac{E}{v}$
3. $RE$
4. $Rv$

Q. In an atom, the two electrons move round the nucleus in circular orbits of radii R and 4R. The ratio of the time taken by them to complete one revolution is

1. $\frac{1}{4}$
2. $\frac{4}{1}$
3. $\frac{8}{1}$
4. $\frac{1}{8}$

Q. Which energy state of the triply ionized beryllium ($B{e}^{3+}$) has the same electron orbital radius as that of the ground state of hydrogen?

1. n = 1
2. n = 2
3. n = 3
4. n = 4

Q.

In any Bohr orbit of the hydrogen atom, the ratio of kinetic energy to potential energy of the electron is

1. 1/2

2. 2
   

3. -1/2
   

4. -2

Q. The ratio of kinetic energy to the total energy of an electron in a Bohr's orbit of the hydrogen atom is

1. 1 : 1
2. 1 : -1
3. 2 : -1
4. 1 : -2

Q. In the Bohr's hydrogen atom model, the radius of the stationary orbit is directly proportional to (n = principle quantum number)

1. $n$
2. $n^{-1}$
3. $n^2$
4. $n^{-2}$

Q. In a Bohr atom the electron is replaced by a particle of mass 150 times the mass of the electron and the same charge. If $a_0$ is the radius of the Bohr orbit, then that of the new atom will be

1. $150a_0$
2. $\sqrt{150}{a}_0$
3. $\frac{a_0}{\sqrt{150}}$
4. $\frac{a_0}{150}$

Q. The average current due to an electron orbiting the proton in the $n^{th}$ Bohr orbit of the hydrogen atom is

1. $\propto n$
2. $\propto n^3$
3. $\propto n^{-3}$
4. None of these