Structure of Atom

(i) Calculate the number of electrons which will together weigh one gram. (ii) Calculate the mass and charge of one mole of electrons.

(i) Calculate the total number of electrons present in one mole of methane. (ii) Find (a) the total number and (b) the total mass of neutrons in 7 mg of 14C. (Assume that mass of a neutron = $1.675 \times 10$⁻²⁷ kg). (iii) Find (a) the total number and (b) the total mass of protons in 34 mg of NH₃ at STP. Will the answer change if the temperature and pressure are changed?

How many neutrons and protons are there in the following nuclei? ¹³₆C, ¹⁶₈O, ²⁴₁₂Mg, ⁵⁶₂₆Fe, ⁸⁸₃₈Sr

Write the complete symbol for the atom with the given atomic number (Z) and atomic mass (A) (i) Z = 17, A = 35. (ii) Z = 92, A = 233. (iii) Z = 4, A = 9.

Yellow light emitted from a sodium lamp has a wavelength (λ) of 580 nm. Calculate the frequency (ν) and wavenumber (ν̄) of the yellow light.

Find energy of each of the photons which (i) correspond to light of frequency $3 \times 10$¹⁵ Hz. (ii) have wavelength of 0.50 Å.

Calculate the wavelength, frequency and wavenumber of a light wave whose period is $2.0 \times 10$⁻¹⁰ s.

What is the number of photons of light with a wavelength of 4000 pm that provide 1J of energy?

A photon of wavelength $4 \times 10$⁻⁷ m strikes on metal surface, the work function of the metal being 2.13 eV. Calculate (i) the energy of the photon (eV), (ii) the kinetic energy of the emission, and (iii) the velocity of the photoelectron (1 eV = $1.6020 \times 10$⁻¹⁹ J).

Electromagnetic radiation of wavelength 242 nm is just sufficient to ionise the sodium atom. Calculate the ionisation energy of sodium in kJ mol⁻¹.

A 25 watt bulb emits monochromatic yellow light of wavelength of 0.57 μm. Calculate the rate of emission of quanta per second.

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. Calculate threshold frequency (ν₀) and work function (W₀) of the metal.

What is the wavelength of light emitted when the electron in a hydrogen atom undergoes transition from an energy level with n = 4 to an energy level with n = 2?

How much energy is required to ionise a H atom if the electron occupies n = 5 orbit? Compare your answer with the ionization enthalpy of H atom (energy required to remove the electron from n = 1 orbit).

What is the maximum number of emission lines when the excited electron of a H atom in n = 6 drops to the ground state?

(i) The energy associated with the first orbit in the hydrogen atom is –$2.18 \times 10$⁻¹⁸ J atom⁻¹. What is the energy associated with the fifth orbit? (ii) Calculate the radius of Bohr’s fifth orbit for hydrogen atom.

Calculate the wavenumber for the longest wavelength transition in the Balmer series of atomic hydrogen.

What is the energy in joules, required to shift the electron of the hydrogen atom from the first Bohr orbit to the fifth Bohr orbit and what is the wavelength of the light emitted when the electron returns to the ground state? The ground state electron energy is –$2.18 \times 10$⁻¹¹ ergs.

The electron energy in hydrogen atom is given by Eₙ = (–$2.18 \times 10$⁻¹⁸)/n² J. Calculate the energy required to remove an electron completely from the n = 2 orbit. What is the longest wavelength of light in cm that can be used to cause this transition?

Calculate the wavelength of an electron moving with a velocity of $2.05 \times 10$⁷ m s⁻¹.