Problem # 11.a) State the;
(i) Heisenberg uncertainty principle.
(ii) Hund’s rule.
(iii) Paul’s Principle.
(iv) Aufbau’s Principle.
Answer
(b) Brief explain why the following sets of quantum numbers are NOT allowed in hydrogen
atom:
(i) n = 1, L = 1, ml = 0
(ii) n = 1, L = 0, ml = 2
(iii) n = 4, L = 3, ml = 4
(iv) n = 0, L = 0, ml = 0 and
(v) n = 2, L = -1, ml = 1
Answer
(c) How many orbitals are there in each of the following sublevel?
(i) 1s
(ii) 2p
(iii) 3d
(iv) 4f
Answer
d) How many sublevels are there in each of the following shells?
(i) K
(ii) N
(iii) L
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(e) Which of the following electronic configuration is correct for 14p in its ground state?
State the principle violated in each case!
Answer
Problem # 12.
(a) Define the following terms.
(i) Quantum orbital
(ii) Quantum numbers
(iii) Quantization of energy
(iv) Wave particle duality of matter
Answer
(b) Give the postulates of bohr's atomic model
Answer
(c) What are the shortcomings of bohr's atomic model?
Answer
Problem # 13.
(a) State the rules which govern the pairing of electrons in orbital of an atom which is in the ground state.
Answer
(b) Calculate the energy associated with an electron moving in an orbital of energy level n=2.
Answer
(c) The mass spectrum of an element enables the relative abundance of each isotope of an element to be determined. Data related to the mass of an element X whose atomic number is 35 appear as follows:
(ii) Write down the conventional symbols for the two isotopes of X
(iii) Calculate the relative atomic mass of X to three significant figures
Answer
Problem # 14.
(a) State
(i) Aufbau principle
(ii) Hund’s rule of maximum multiplicity
(iii) the uncertainty principle
Answer
(b) (i) What is an atomic spectrum?
(ii) How does an atomic spectrum differ from a continuous spectrum?
Answer
(c) The wave length of the lines in the Balmer series of the hydrogen spectrum is given by the
expression 1/λ=RH(1/2²– 1/n²) where RH is a constant and n is an integer greater than 2.
(i) Draw an energy level diagram to show the origin of the first and third lines in the Balmer series.
(ii) Calculate the wavelength of the first line in 1.(c)(i) above.
Answer
Problem # 15.
(a)
(i) Outline the fundamental postulates of Plank’s quantum theory
(ii) What does the term wave-particle duality nature of an electron mean?
(iii) State the uncertainty principle
Answer
(b) Calculate the energy of a photon of radiation whose wave length is 5.89x10^-5 cm emitted
from sodium atoms when heated.
Answer
Problem # 16.
(a) The mass number of two atoms X and Y with the same atomic numbers 206 and 208 respectively. If X contains 124 neutrons in its nucleus, Find the number of neutrons in the nucleus of Y. What is the atomic number of Y?.
Answer
(b) The element Europium, Eu exists in nature as two isotopes, ¹5¹Eu with a mass of 150.91976 a.m.u and ¹5³Eu with a mass of 152.9196 a.m.u, if the average atomic mass of europium is 51.96 a.m.u calculate the percentage relative abundances of the two isotopes.
Answer
Problem # 17.
When an electron jumps from a certain higher energy level E2, to its ground state E1, green light in the Balmer series is emitted. If the energy released during this transition is 4.071×10^19J. Determine the;
(i) Wavelength of the green light.
(ii) Higher energy level E2, from which the electron jumps to the ground energy level E1.
Answer
Problem # 18.
The following figure shows the mass spectrum of lead, the highest peaks and the mass numbers are shown. Calculate the average atomic mass of lead.
Problem # 19.
(a) Lyman discovered a series of spectral lines for hydrogen in the ultra violet region of the electromagnetic spectrum. What value must n1 have for this series? Give the reason for your answer.
Answer
(b) Calculate the energy of a line in the lyman series with n1= 1 and n2=⅃∞
Answer
(c) An experimental iodine laser emits light of wavelength 1.315μm. Calculate the frequency of this light and the energy per photon.
Answer
Problem # 20.
(a) Write the atomic number of an atom with the electronic configuration of 1s² 2s² 2p6 3s² 3p5.
Answer
(b) X occurs naturally as
37 35
X and X. Given that the relative atomic mass of X is 35.5, determine the percentage of
37 35
X and X in the sample of element X.
Answer
(c) "The motion of an electron in an atom is not a simple rotation around an orbit, but rather a three dimensional standing wave which obeys Schröndinger equation".
(i) In which atomic model is this statement based?
(ii) Name other two atomic models that attempt to explain the structure of an atom.
Answer
Problem # 21.
(a) Describe the dual nature of electromagnetic radiation and wave particle duality.
Answer
(b) Calculate the velocity of an electron whose wavelength is 10^-9 metres.
Answer
(c) Arrange the following coloured lights in order of increasing wavelength. Green, blue, red, violet, yellow.
Answer
(d) With reference to prism of spectrometer, explain the term frequency of a line.
Answer
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