Atoms

In the first excited state of hydrogen atom, the energy of its electron is −3.4 eV. The radial distance of the electron from the hydrogen nucleus in this case is approximately : (Take 1 eV = 1.6 10-19 J, e = 1.6 10-19 C and 14 0 = 9 109 N m2/C2)

1. 2.1 10-8 m
2. 2.1 10-10 m
3. 2.1 10-11 m
4. 2.1 10-9 m

Consider that an electron is revolving in an excited state of Hydrogen atom with velocity 25.6 105 ms-1. The radius of the orbit is x 10-9 m. The value of x is: [Take the mass of electron to be 9 10-31 kg, charge of electron = -1.6 10-19 C and 14 0 = 9 109 Nm2C-2]

1. 1
2. 4
3. 3
4. 2

In Geiger-Marsden experiment, the number of scattered -particles N( ) is plotted as a function of scattering angle . Which of the following options represents the correct plot?

1. [figure]
2. [figure]
3. [figure]
4. [figure]

A particle of mass m is moving around the origin with a constant force F pulling it towards the origin. If Bohr model is used to describe its motion, the radius of the nth orbit and the particle's speed v in the orbit depend on n as

1. r n2/3; v n1/3
2. r n4/3; v n-1/3
3. r n1/3; v n1/3
4. r n1/3; v n2/3

De-Broglie wavelength of an electron orbiting in the n = 2 state of hydrogen atom is close to (Given Bohr radius = 0.052 nm)

1. 1.67 nm
2. 2.67 nm
3. 0.067 nm
4. 0.67 nm

Given below are two statements: In the light of the above statements, choose the most appropriate answer from the options given below.

1. Both Statement I and Statement II are correct
2. Both Statement I and Statement II are incorrect
3. Statement I is correct but Statement II is incorrect
4. Statement I is incorrect but Statement II is correct

The spectral series which corresponds to the electronic transition from the levels n2 = 5, 6, to the level n1 = 4 is

1. Pfund series
2. Brackett series
3. Lyman series
4. Balmer series

Some energy levels of a molecule are shown in the figure with their wavelengths of transitions. Then : [figure]

1. 3 > 2, 1 = 2 2
2. 3 > 2, 1 = 4 2
3. 1 > 2, 2 = 2 3
4. 2 > 1, 2 = 2 3

In hydrogen spectrum, the shortest wavelength in the Balmer series is . The shortest wavelength in the Brackett series is :

1. 4
2. 9
3. 16
4. 2

The radius of inner most orbit of hydrogen atom is 5.3 10-11 m. What is the radius of third allowed orbit of hydrogen atom?

1. 1.06 Å
2. 1.59 Å
3. 4.77 Å
4. 0.53 Å

Let T1 and T2 be the energy of an electron in the first and second excited states of hydrogen atoms, respectively. According to the Bohr's model of an atom, the ratio T1 : T2 is

1. 1 : 4
2. 4 : 1
3. 4 : 9
4. 9 : 4

Let R1 be the radius of the second stationary orbit and R2 be the radius of the fourth stationary orbit of an electron in Bohr's model. The ratio R1R2 is :

1. 4
2. 0.25
3. 0.5
4. 2

For which one of the following, Bohr model is not valid?

1. Singly ionised helium atom (He+)
2. Deuteron atom
3. Singly ionised neon atom (Ne+)
4. Hydrogen atom

-particle consists of :

1. 2 electrons, 2 protons and 2 neutrons
2. 2 electrons and 4 protons only
3. 2 protons only
4. 2 protons and 2 neutrons only

The total energy of an electron in an atom in an orbit is -3.4 eV. Its kinetic and potential energies are, respectively.

1. 3.4 eV, -6.8 eV
2. 3.4 eV, 3.4 eV
3. -3.4 eV, -3.4 eV
4. -3.4 eV, -6.8 eV

The ratio of kinetic energy to the total energy of an electron in a Bohr orbit of the hydrogen atom, is

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

The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is

1. 1
2. 4
3. 0.5
4. 2

Given the value of Rydberg constant is 107 m-1, the wave number of the last line of the Balmer series in hydrogen spectrum will be

1. 0.25 107 m-1
2. 2.5 107 m-1
3. 0.025 104 m-1
4. 0.5 107 m-1

When an -particle of mass m moving with velocity v bombards on a heavy nucleus of charge Ze, its distance of closest approach from the nucleus depends on m as

1. 1m2
2. m
3. 1m
4. 1 m

Electrons of mass m with de-Broglie wavelength fall on the target in an X-ray tube. The cutoff wavelength ( 0) of the emitted X-ray is

1. 0 = 2mc 2h
2. 0 = 2hmc
3. 0 = 2m2c2 3h2
4. 0 =

If an electron in a hydrogen atom jumps from the 3rd orbit to the 2nd orbit, it emits a photon of wavelength . When it jumps from the 4th orbit to the 3rd orbit, the corresponding wavelength of the photon will be

1. 1625
2. 916
3. 207
4. 2013

In the spectrum of hydrogen, the ratio of the longest wavelength in the Lyman series to the longest wavelength in the Balmer series is

1. 275
2. 527
3. 49
4. 94

Consider 3rd orbit of He+ (Helium), using non-relativistic approach, the speed of electron in this orbit will be [given K = 9 109 constant, Z = 2 and h (Planck's Constant) = 6.6 10-34 J s]

1. 0.73 106 m/s
2. 3.0 108 m/s
3. 2.92 106 m/s
4. 1.46 106 m/s

Hydrogen atom in ground state is excited by a monochromatic radiation of = 975 A. Number of spectral lines in the resulting spectrum emitted will be

1. 3
2. 2
3. 6
4. 10

Ratio of longest wave lengths corresponding to Lyman and Balmer series in hydrogen spectrum is

1. 729
2. 931
3. 527
4. 323

An electron in hydrogen atom makes a transition n1 n2 where n1 and n2 are principal quantum numbers of the two states. Assuming Bohr's model to be valid, the time period of the electron in the initial state is eight times that in the final state. The possible values of n1 and n2 are

1. n1 = 6 and n2 = 2
2. n1 = 8 and n2 = 1
3. n1 = 8 and n2 = 2
4. n1 = 4 and n2 = 2

The transition from the state n = 3 to n = 1 in a hydrogen like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from

1. 2 1
2. 3 2
3. 4 2
4. 4 3

Electron in hydrogen atom first jumps from third excited state to second excited state and then from second excited to the first excited state. The ratio of the wavelengths 1 : 2 emitted in the two cases is

1. 75
2. 2720
3. 275
4. 207

An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be

1. 24hR25m
2. 25hR24m
3. 25m24hR
4. 24m25hR

An electron in the hydrogen atom jumps from excited state n to the ground state. The wavelength so emitted illuminates a photosensitive material having work function 2.75 eV. If the stopping potential of the photoelectron is 10 V, then the value of n is

1. 2
2. 3
3. 4
4. 5