Helium atom can be excited to 1s¹, 2p¹ configuration by light of 58.44 nm. The lowest excited state with configuration 1s¹, 2s¹ lies 4857 cm^-1 (1/$\mathrm{\lambda }$) below the 1s¹, 2p¹ state. What would be the average He - H bond energy so that HeH₂ could form, non-endothermically from the lowest excited singlet state of helium? Neglect any difference between $∆$G and $∆$H and take $∆$H as 218 kJ mol^-1

The number of electrons in one molecule of CO₂ are - 

The ion that is isoelectronic with CO is-

If frequency of the X-rays produced using an element as anti-cathode is found to be 2500 sec^-1, the atomic number of used element is (a, b= 1)

What is the energy required per mole to excite an electron from the third to fifth Bohr orbit in hydrogen ?

The energy of electron in first Bohr's orbit of H-atom is -13.6 eV. What will be its potential energy in n = 4.

Sodium atoms can be ionised by supplying an energy of 118 kcal mol^-1. Using this data, calculate the lowest possible frequency of light that can ionise a sodium atom.

(h = 6.624 x 10^-27 erg.sec, c= 3 x 10¹⁰ cm sec^-1).

A glow worm of mass 5.0 g emits red light (650 nm) with a power of 0.1 W. entirely in the backward direction. What velocity would it accelerate to after 10 years, if released in free space (and assumed to be alive)?

Which of the following postulates does not belong to Bohr's model of the atom?

The total number of orbitals having l = 3  is - 

Bohr's atomic model can explain:-

The presence of one electron each in the three 2p sub-shell of nitrogen is explained by 

When the atoms of gold sheet are bombarded with a beam of $\alpha$ -particles, only a few a-particles get deflected where as most of them go straight undeflected. This is because

Using radiation of wavelength 3500 Å, it is observed that the maximum kinetic energy of the emitted photoelectrons is 1.6 eV for potassium. Calculate the work function of the metal. [h=6.626 x 10^-34 Js, 1 eV=1.6 x 10^-19 J]

To give designation to an orbital, we need

The rest mass of a proton is 1.673 x 10^-27 kg and that of the electron is 9.109 x 10^-31 kg. What must be the speed of the proton which has the same de Broglie wavelength as an electron moving with a speed of 9 x 10⁶ m/s?

Which one of the following statement is not true about the quantum numbers n, l, m and s

The number of electrons in the valence shell of calcium is 

The brackett series of spectral lines arise when an electron in an excited hydrogen atom jumps from an energy level

What is the ratio of the time period of revolution of electron He⁺ ion sample in the orbit where the path length is three time the de-broglies wavelength to the time period of revolution in the ground state –

The ratio of the wavelengths of the last lines of the Balmer and Lyman series is-

The energy of the emitted photon when an electron in $B{e}^{3+}$ ion returns from n=2 level to the ground state is 

The splitting of spectral lines in a magnetic field, arising out of the orbital motion of electrons only and the further splitting due to spin motion are respectively called

A photon of wavelength 300 nm causes the emission of two photons. If the wavelength of one of them is 700 nm. What is the wavelength of the other photon?

The electronic transition in the hydrogen atom that emits maximum energy is:

The spectrum of He-atom may be considered similar to the spectrum of - 

The Compton wavelength for an electron is  $\left(\frac{h}{m_{0}c}\right)$

calculate $∆\lambda$= $\left(\frac{h}{m_{0}c}\right)$(1- cos θ) for a scattering angle  θ = $\mathrm{\pi }$/3. What is the maximum value for $∆\lambda$ ?

2. 0.012 Å, 0.048 Å

The total spin resulting for a 3d⁷ configuration is 

Supposing the energy of the fourth shell for the hydrogen atom is -50a.u. (Arbitrary unit). What would be its ionization potential-

An element with atomic mass Z consists of two isotopes of mass number Z-1 and Z + 2. The percentage abundance of the heavier isotope is -