Two isotopes of Boron are found in the nature with atomic weights 10.01(I) and 11.01(II). The atomic weight of natural Boron is 10.81. The percentage of (I) and (II) isotopes in it are respectively-

Calculate the wavenumber of lines having the frequency of 5 x 10¹⁶ cycles per sec. 

Which of the following set of quantum number is not valid

For particles having same kinetic energy, the de Broglie wavelength is-

Photochemical dissociation of oxygen results in the production of two oxygen atoms, one in the ground state and one in the excited state.

O₂ $\stackrel{\mathrm{hv}}{\to }$ O→O*

The maximum wavelength () needed for this is 174 nm. If the excitation energy O→O* is 3.15 x 10^-19 J. How much energy in kJ mole^-1 is needed for the dissociation of one mole of oxygen into normal atoms in ground state?

Rutherford's scattering experiment is related to the size of the-

The  energy needed to convert helium atom  to He ⁺² is -79eV. The first ionization energy of this atom is about 

Elements upto atomic number 103 have been synthesized and studied. If a newly discovered element is found to have an atomic number 106, its electronic configuration will be -

The most probable radius (in pm) for finding the electron in He⁺ is -

The mass ratio of photons corresponding to the first lines of the Lymann and the Balmer series of the atomic spectrum of hydrogen is :

An electron, practically at rest, is initially accelerated through a potential difference of 100 volts. It then has a de Broglie wavelength=$\lambda$₁Å. It then get retarded through 19 volts and then it has wavelength $\lambda$₂ Å. A further retardation through 32 volts changes the wavelength to $\lambda$₃.

What is ($\lambda$₃-$\lambda$₂)/$\lambda$₁?

Which of the following has the maximum number of  unpaired electons-

There are three energy levels in an atom. How many spectral lines are possible in its emission spectra?

Azimuthal quantum number defines -

For the energy levels in an atom, which one of the following statements is correct -

Arrange the following particles in increasing order of values of e/m ratio: Electron(e), proton(p), neutron(n) and α-particle(α)

The increasing order of energy of electromagnetic radiation can be represented as

The wavelength of the photoelectric threshold of metal is 230 nm. Determine the K.E. of photoelectron ejected from the surface by UV radiation emitted from the second-longest wavelength transition (downward) of an electron in Lyman series of the atomic spectrum of hydrogen. (R=1.09677 x 107 m^-1)

Beryllium's fourth electron will have the four quantum numbers :

                         n               $\mathcal{l}$               m             s

Mass of neutron is ........................times the mass of an electron-

If the size of the first orbit of the hydrogen atom is 5.29 nm, the size of the second orbit of He⁺ is

Which one of the following is not the characteristic of Planck's quantum theory of radiation –

 3p orbital has -

An isotone of ₃₂Ge⁷⁶ is:

(i) ₃₂Ge⁷⁷ 

(ii) ₃₃As⁷⁷ 

(iii) ₃₄Se⁷⁷ 

(iv) ₃₄Se⁷⁸ 

Which of the following has greater number of electrons than neutrons?

The work function of a metal is 4.2 eV. If radiations of 2000 $A^0$ fall on the metal then the kinetic energy of the fastest photoelectron is 

The relationship between energy E, of the radiation with a wavelength 8000 $A^0$ and the energy of the radiation with a wavelength 16000 $A^0$ is 

The transition of electrons in H atom that will emit maximum energy is:

The transition in the He⁺ ion in the balmer series that would have the same wave number as the first Lyman line in the hydrogen spectrum is-

If the speed of electron in Bohr's first orbit of hydrogen atom be x, then speed of the electron in 3rd orbit is: