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Chapter: 11th Chemistry : Quantum Mechanical Model of Atom

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Brief questions and answers: Chemistry: Quantum Mechanical Model of Atom

Chemistry : Quantum Mechanical Model of Atom


26. Which quantum number reveal information about the shape, energy, orientation and size of orbitals?


27. How many orbitals are possible for n =4?


n = 4   l = 0, 1, 2, 3

four sub-shells s, p, d, f

l = 0ml = 0 ; one 4s orbital.

l = 1 ml = –1, 0, +1 ; three 4p orbitals.

l = 2 ml = –2, –1, 0, +1, +2 ; five 4d orbitals.

l = 3 ml = -3, –2, –1, 0, +1, +2 , +3; seven 4f orbitals

Over all Sixteen orbitals.


28. How many radial nodes for 2s, 4p, 5d and 4f orbitals exhibit? How many angular nodes?



29. The stabilisation of a half filled d - orbital is more pronounced than that of the p-orbital why?


30. Consider the following electronic arrangements for the d5 configuration.

(i) which of these represents the ground state

(ii) which configuration has the maximum exchange energy.



31. State and explain pauli's exclusion principle.


32. Define orbital? what are the n and l values for 3px and 4dx2-y2 electron?



33. Explain briefly the time independent schrodinger wave equation?


34. Calculate the uncertainty in position of an electron, if Δv = 0.1% and υ = 2.2 x106 ms-1



35. Determine the values of all the four quantum numbers of the 8th electron in O- atom and 15th electron in Cl atom and the last electron in chromium



36. The quantum mechanical treatment of the hydrogen atom gives the energy value:

i) use this expression to find ΔE between n = 3 and m=4

ii) Calculate the wavelength corresponding to the above transition.



37. How fast must a 54g tennis ball travel in order to have a de Broglie wavelength that is equal to that of a photon of green light 5400Å?



38. For each of the following, give the sub level designation, the allowable m values and the number of orbitals

i) n = 4, l =2, ii) n =5, l = 3 iii) n=7, l=0



39. Give the electronic configuration of Mn2+ and Cr3+


40. Describe the Aufbau principle


41. An atom of an element contains 35 electrons and 45 neutrons. Deduce

i) the number of protons

ii) the electronic configuration for the element

iii) All the four quantum numbers for the last electron



42. Show that the circumference of the Bohr orbit for the hydrogen atom is an integral multiple of the de Broglie wave length associated with the electron revolving arround the nucleus.


43. Calculate the energy required for the process.

He+ (g) → He2+ (g) + e-

The ionisation energy for the H atom in its ground state is - 13.6 ev atom-1.



44. An ion with mass number 37 possesses unit negative charge. If the ion contains 11.1% more neutrons than electrons. Find the symbol of the ion.



45. The Li2+ ion is a hydrogen like ion that can be described by the Bohr model. Calculate the Bohr radius of the third orbit and calculate the energy of an electron in 4th orbit.



46. Protons can be accelerated in particle accelerators. Calculate the wavelength (in Å) of such accelerated proton moving at 2.85 ×108 ms-1 ( the mass of proton is 1.673 × 10-27 Kg).



47. What is the de Broglie wavelength (in cm) of a 160g cricket ball travelling at140 Km hr-1.



48. Suppose that the uncertainty in determining the position of an electron in an orbit is 0.6 Å. What is the uncertainty in its momentum?



49. Show that if the measurement of the uncertainty in the location of the particle is equal to its de Broglie wavelength, the minimum uncertainty in its velocity is equal to its velocity / 4π



50. What is the de Broglie wave length of an electron, which is accelerated from the rest, through a potential difference of 100V?



51. Identify the missing quantum numbers and the sub energy level


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