ISC (Science) ISC Class 12 - CISCE Important Questions

In Bohr’s model of the hydrogen atom, the radius of the first orbit of an electron is r₀ . Then, the radius of the third orbit is:

a) `r_0/9`

b) `r_0`

c) `3r_0`

d) `9r_0`

Calculate the minimum wavelength of the spectral line present in Balmer series of hydrogen

if `E_p` and `E_k` represent potential energy and kinetic energy respectively, of an orbital electron, then, according to B9hr's theory:

a)`E_k = -E_p"/"2`

b) `E_k = -E_p`

c) `E_k = -2E_p`

d) `E_k = 2E_p`

Name the series in the atomic spectra of the hydrogen atom that falls in the ultra violet region. 

State any two Bohr’s postulates and write the energy value of the ground state of the hydrogen atom. 

According to Bohr, 'Angular momentum of an orbiting electron is quantized'. What is meant by this statement?

When a beam of white light is passed through sodium vapors and then through a spectrometer, spectrum so obtained has two dark lines present in the yellow region. This spectrum is called:

If l₃ and l₂ represent angular momenta of an orbiting electron in III and II Bohr orbits respectively, then l₃: l₂ is :

The total energy of an electron in the ground state of the hydrogen atom is -13·6 eV. Its total energy, when a hydrogen atom is in the first excited state, is ______.

Calculate angular momentum of an electron in the third Bohr orbit of a hydrogen atom.

Draw energy level diagram for a hydrogen atom, showing the first four energy levels corresponding to n=1, 2, 3 and 4. Show transitions responsible for:
(i) Absorption spectrum of Lyman series.
(ii) The emission spectrum of the Balmer series.

How are various lines of Lyman series formed? Explain on the basis of Bohr’s theory.

The first line of Balmer series (H_α) in the spectrum of hydrogen is obtained when an electron of hydrogen atom goes from ______.

Name the series of lines of hydrogen spectrum which lie in the ultraviolet region.

Name the series of lines of hydrogen spectrum which lie in the visible region.

How much is the angular momentum of an electron when it is orbiting in the second Bohr orbit of hydrogen atom?

Using Bohr’s Theory of hydrogen atom, obtain an expression for the velocity of an electron in the n^th orbit of an atom.

The figure below is the Energy level diagram for the Hydrogen atom. Study the transitions shown and answer the following question:

1. State the type of spectrum obtained.
2. Name the series of spectrum obtained.

On the basis of Bohr's theory, derive an expression for the radius of the n^th orbit of an electron of hydrogen atom.

State the Bohr's postulate of angular momentum of an electron.