Bohr model - postulates, electron energy and limitations — practice questions

Question 1 · difficulty L2 · understanding

The energy of an electron in the first Bohr orbit of the H-atom is -13.6 eV. The magnitude of energy value of an electron in the first excited state of Be 3+ is ________ eV (nearest integer value).

Question 2 · difficulty L2 · understanding

For hydrogen atom, energy of an electron in first excited state is $$-3.4 \mathrm{~eV}, \mathrm{K} . \mathrm{E}$$. of the same electron of hydrogen atom is $$x \mathrm{~eV}$$. Value of $$x$$ is _________ $$\times 10^{-1} \mathrm{~eV}$$. (Nearest integer)

Question 3 · difficulty L2 · understanding

Assume that the radius of the first Bohr orbit of hydrogen atom is 0.6 $$\mathrm{\mathop A\limits^o }$$. The radius of the third Bohr orbit of He$$^+$$ is __________ picometer. (Nearest Integer)

Question 4 · difficulty L2 · understanding

The Bohr radius of a hydrogen like species is 70.53 pm . The species and the stationary state (n) are respectively (Given : Hydrogen atom Bohr radius is 52.9 pm )

• A. $\mathrm{Li}^{2+}, 3$
• B. $\mathrm{He}^{+}, 3$
• C. $\mathrm{He}^{+}, 2$
• D. $\mathrm{Li}^{2+}, 2$

Question 5 · difficulty L2 · understanding

The species having identical radii according to the Bohr's theory are : A. H (first orbit) B. $\mathrm{He}^{+}$(first orbit) C. $\mathrm{He}^{+}$(Second orbit) D. $\mathrm{Li}^{2+}$ (first orbit) E. $\mathrm{Be}^{3+}$ (Second orbit) Choose the correct answer from the options given below :

• A. A and C Only
• B. A and E Only
• C. B and E Only
• D. C and D Only

Question 6 · difficulty L2 · understanding

What is the energy (in J atom −1 ) required for the following process? Li 2+ (g) → Li 3+ (g) + e − (Take the ionization energy for the H atom in the ground state as $2.18 \times 10^{−18} \text{ J atom}^{−1}$)

• A. $8.72 \times 10^{−18}$
• B. $1.962 \times 10^{−18}$
• C. $1.962 \times 10^{−17}$
• D. $6.54 \times 10^{−17}$

Question 7 · difficulty L2 · understanding

The energy required by electrons, present in the first Bohr orbit of hydrogen atom to be excited to second Bohr orbit is $\_\_\_\_$ $\mathrm{J} \mathrm{mol}^{-1}$. Given: $R_H=2.18 \times 10^{-11} \mathrm{ergs}$.

• A. $9.835 \times 10^{12}$
• B. $1.635 \times 10^{-11}$
• C. $1.635 \times 10^{-18}$
• D. $9.835 \times 10^5$

Question 8 · difficulty L2 · understanding

Which of the following postulate of Bohr's model of hydrogen atom is not in agreement with quantum mechanical model of an atom?

• A. The electron in a H atom's stationary state moves in a circle around the nucleus.
• B. An atom can take only certain distinct energies $\mathrm{E}_1, \mathrm{E}_2, \mathrm{E}_3$, etc. These allowed states of constant energy are called the stationary states of atom.
• C. An atom in a stationary state does not emit electromagnetic radiation as long as it stays in the same state.
• D. When an electron makes a transition from a higher energy stationary state to a lower energy stationary state, then it emits a photon of light.

Question 9 · difficulty L2 · understanding

According to Bohr's model of hydrogen atom, which of the following statement is incorrect?

• A. Radius of $4^{\text {th }}$ orbit is four times larger than that of $2^{\text {nd }}$ orbit
• B. Radius of $8^{\text {th }}$ orbit is four times larger than that of $4^{\text {th }}$ orbit
• C. Radius of $6^{\text {th }}$ orbit is three times larger than that of $4^{\text {th }}$ orbit
• D. Radius of $3^{\text {rd }}$ orbit is nine times larger than that of $1^{\text {st }}$ orbit

Question 10 · difficulty L2 · understanding

Radius of the first excited state of Helium ion is given as : $\mathrm{a}_0 \rightarrow$ radius of first stationary state of hydrogen atom.

• A. $\mathrm{r}=\frac{\mathrm{a}_0}{4}$
• B. $\mathrm{r}=2 \mathrm{a}_0$
• C. $\mathrm{r}=4 \mathrm{a}_0$
• D. $\mathrm{r=\frac{a_0}{2}}$