Bohr's Model of Atom

Q.

If $e$ is the electronic charge, $c$ is the speed of light in free space and $h$ is Plancks constant, the quantity $\frac{1}{4{\mathrm{\pi \epsilon }}_0}\frac{e^2}{hc}$ has dimensions of:

1. $\left[L{C}^{-1}\right]$

2. $\left[M^0{L}^0{T}^0\right]$

3. $\left[ML{T}^0\right]$

4. $\left[ML{T}^{-1}\right]$

Q.

Atomic radii of Fluorine and Neon in Angstrom unit are respectively given by

1. $1.60,1.60$

2. $0.75,1.60$

3. $1.60,0.72$

4. $0.72,0.72$

Q. The electron moves to a higher energy level, the excited state when

1. a proton gains energy
2. an electron loses energy
3. an electron gains energy
4. a proton loses energy

Q.

Consider the diffraction pattern obtained from the sunlight incident on a pinhole of diameter $0.1\mu m$. If the diameter of the pinhole is slightly increased, it will affect the diffraction pattern such that

1. its size decreases, but intensity increases

2. its size increases, but intensity decreases

3. its size increases, and intensity increases

4. its size decreases, and intensity decreases

Q.

An electron from various excited states of hydrogen atom emit radiation to come to the ground state. Let ${\mathrm{\lambda }}_{\mathrm{n}},{\mathrm{\lambda }}_{\mathrm{g}}$ be the de Broglie wavelength of the electron in the ${\mathrm{n}}^{\mathrm{th}}$state and the ground state respectively. Let ${\mathrm{A}}_{\mathrm{n}}$ be the wavelength of the emitted photon in the transition from the ${\mathrm{n}}^{\mathrm{th}}$ state to the ground state. For large $\mathrm{n}$, ($\mathrm{A},\mathrm{B}$ are constants)

1. $\wedge {{}^2}_{\mathrm{n}}\approx \hspace{0.17em}\mathrm{A}+{{\mathrm{B\lambda }}^2}_{\mathrm{n}}$

2. $\wedge {}^2\mathrm{n}\approx \mathrm{\lambda }$

3. $\wedge {}_{\mathrm{n}}\approx \mathrm{A}+\left(\mathrm{B}/{{\mathrm{\lambda }}^2}_{\mathrm{n}}\right)$

4. $\wedge {}_{\mathrm{n}}\approx \mathrm{A}+{\mathrm{B\lambda }}_{\mathrm{n}}$

Q.

Positive deviation from ideal gas behavior takes place because of

1. Finite atomic size and $\frac{PV}{nRT}<1$
2. Molecular interaction and $\frac{PV}{nRT}>1$
3. Molecular interaction and $\frac{PV}{nRT}<1$
4. Finite atomic size and $\frac{PV}{nRT}>1$

Q. How to find no.of spectral lines for hydrogen atom

Q. How many elliptical orbits were added by Sommerfeld in the third orbit of the Bohr's atomic model?

1. One
2. Two
3. Three
4. Seven

Q. What are the main postulates of Bohr's theory of an atom ?

Q.

The atomic hydrogen emits a line spectrum consisting of various series. Which series of hydrogen atomic spectra lie in the visible region?

1. Balmer series

2. Lyman series

3. Brackett series

4. Paschen series

Q.

A)explain all the postulates of Bohr's atomic model.(short points).

B) explain draw backs of Rutherford's model of atom.(short points).

Q. When an electron jumps from the ground state to an excited state, it emits energy.

1. True
2. False

Q.

Do electrons have momentum

Q.

In the Bohr model of the hydrogen atom, radiation is emitted when the electron?

Q.

Find the velocity (ms ⁻¹ ) of an electron in the first Bohr orbit of radius $A_0$. Also, Find the De Broglie wavelength (In m). Find the orbital angular momentum of the 2p orbital of the hydrogen atom in units of $\frac{h}{2\pi }$.

Q.

What is Antimatter

Q. By fusing one deuterium nucleus in a hydrogen like species its wave number for a spectral line increases 16/9 times , the atomic number of hydrogen like species is :- (A) 5 (B) 4 (C) 3 (D) 2

Q. The maximum number of electrons that can be accommodated in a shell is given by the formula .

1. ${\text{n}}^2$
2. ${\text{2n}}^2$
3. ${\text{n}}^2$+1

Q.

According to mole concept it says that a standard volume i.e 22.4 liters of gas contains 1 mole right?

And one mole contains 6.023*10²³ right sir so then how did they come to know this, means as if they counted each and every atom or molecule ?

So please explain about this sir.

Q. Assertion: Energy of electron is taken negative. Reason: Energy of electron at infinity is zero.

Q.

Drive an expression for the magnetic moment of an electron revolving around the nucleus in term of its angular momentum what is the direction of magnetic moment of the electron with respect to its angular momentum

Q.

The path around the nucleus in which electrons revolve is called orbits.

1. True
2. False

Q.

Do electrons have a fixed wavelength?

Q.

The fixed paths along which the electrons are revolving around the nucleus are called ___(orbits/curviller\near path).

Q.

An electromagnetic radiation of wavelength 242 nm is just sufficient to ionize a sodium atom. Calculate the ionization energy of sodium in kJ ${mol}^{-1}$.

1. 294.5 KJ mol^-1

2. 394.5 KJ mol^-1

3. 494.5 KJ mol^-1

4. 594.5 KJ mol^-1

Q. (a) As long as an electron revolves in a particular orbit, the electron does not lose its energy. Therefore, these orbits are called stationary orbits and the electrons are said to be in stationary energy states.
(b) Each orbit or shell is associated with a definite amount of energy. Hence these are also called energy levels.
(c) An electron jumps from a lower energy level to a higher energy level, by absorbing energy. It jumps from a higher energy level to a lower energy level, by emitting energy in the form of electromagnetic radiation.
(d) Electrons move around the nucleus in specified circular paths called orbits or shells or energy levels and are designated as K, L, M, N shells respectively.

1. d a c b
2. d b a c
3. d a b c
4. b d a c

Q.

List the factors on which the rate of emission depends?

Q.

The radius of first Bohr's orbit in H-atoms is $r_1$. The corresponding wavelength of an electron in 2nd orbit is:

1. 2πr₁

2. 4πr₁

3. 3πr₁

4. 6πr₁

Q. The radius of the first Bohr orbit of hydrogen atom is $0.59\stackrel{o}{A}$. The radius of the third orbit of $H{e}^{+}$ will be:

1. $1.59\stackrel{o}{A}$
2. $8.46\stackrel{o}{A}$
3. $2.38\stackrel{o}{A}$
4. $0.705\stackrel{o}{A}$

Q.

Which of the following are true according to the postulates of Bohr's theory?

1. When an atom gets the required energy from outside, it jumps from lower orbits to higher orbits and remains there

2. When an atom gets the required energy from outside, it jumps from lower orbits to higher orbits and remains there for very short intervals of time and returns back to the lower orbit, radiating energy

3. Angular momentum of an electron is proportional to n

4. Angular momentum of an electron is independent of n