Atoms

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