The number of electrons in the valence shell of sulphur in SF₆ is :

• 12

• 10

• 8

• 11

Rutherford's experiment on the scattering of α-particles showed for the first time that the atom has:

• electrons

• protons

• nucleus

• neutrons

For a Bohr atom angular momentum M of the electron is : (n = 0, 1, 2......)

• $\frac{{\mathrm{nh}}^2}{4\mathrm{\pi }}$

• $\frac{{\mathrm{n}}^2{\mathrm{h}}^2}{4\mathrm{\pi }}$

• $\frac{\sqrt{{\mathrm{nh}}^2}}{4\mathrm{\pi }}$

• $\frac{\mathrm{nh}}{2\mathrm{\pi }}$

The radius of hydrogen atom in the ground state is 0.53 Å. The radius of Li²⁺ ion (atomic number = 3) in a similar state is :

• 0.176 Å

• 0.30 Å

• 0.53 Å

• 1.23 Å

The wavelength of the radiation emitted, when in a hydrogen atom electron falls from infinity to stationary state 1, would be (Rydberg constant = 1.097 × 10⁷ m^-1)

• 91 nm

• 192 nm

• 406 nm

• 9.1 × 10^-8 nm

The radioactive isotope ${}_{27}{}^{60}\mathrm{Co}$ which is used in the treatment of cancer can be made by (n, p) reaction. For this reaction the target nucleus is

• ${}_{28}{}^{59}\mathrm{Ni}$

• ${}_{27}{}^{59}\mathrm{Co}$

• ${}_{28}{}^{60}\mathrm{Ni}$

• ${}_{27}{}^{60}\mathrm{Co}$

The energy of second Bohr orbit of the hydrogen atom is -328 kJ mol^-1; hence the energy of fourth Bohr orbit would be

• -41 kJ mol^-1

• -1312 kJ mol^-1

• -164 kJ mol^-1

• -82 kJ mol^-1

If the energy difference between the ground state of an atom and its excited state is 4.4× 10^-4J, the wavelength of photon required to produce the transition :

• 2.26 × 10^-12m

• 1.13 × 10^-12m

• 4.52× 10^-16m

• 4.52 × 10^-12m

Which of the following sets of qunatum numbers correct?

• n =5, l=4, m=0, s=+1/2

• n= 3, l=3, m=+3, s= +1/2

• n=6, l=0, m=+1, s= =1/2

• n=4, l= 2, m=+2, s=0

An electron from one Bohr stationary orbit can go to next higher orbit

• by emission of electromagnetic radiation

• by absorption of any electromagnetic radiation

• by absorption of electromagnetic radiation of particular frequency

• without emission or absorption of electromagnetic radiation