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Practice each question, then open the answer or worked solution.
Total number of orbitals associated with the third shell will be __________.
(i) 2
(ii) 4
(iii) 9
(iv) 3
Ans: (iii) 9
The total number of orbitals is given by n2,where n is the principal quantum number or the principal shell.
Thus for the third shell number of orbitals is 32 i.e. 9
Orbital angular momentum depends on __________.
(i) l
(ii) n and l
(iii) n and m
(iv) m and s
Ans: (i) l
“l” which is known as Azimuthal quantum number or orbital angular momentum or subsidiary quantum number depicts the three dimensional shape of the orbital.
Chlorine exists in two isotopic forms, Cl-37 and Cl-35 but its atomic mass is 35.5. This indicates the ratio of Cl-37 and Cl-35 is approximately
(i) 1:2
(ii) 1:1
(iii) 1:3
(iv) 3:1
Ans: (iii) 1:3
The chlorine is a mixture of two isotopes with atomic masses 37U and 35U and its atomic mass is 35.5U. The atomic mass depicts that % composition of Cl-35 is much higher than that of Cl-37 and they are present in the ratio 1:3.
The pair of ions having the same electronic configuration is __________.
(i) Cr3+, Fe3+
(ii) Fe3+, Mn2+
(iii) Fe3+, Co3+
(iv) Sc3+, Cr3+
Ans: (ii) Fe3+, Mn2+
Fe3+ electronic configuration is 1s2 2s2 2p6 3s2 3p6 3d5 4s2
Mn2+electronic configuration is 1s2 2s2 2p6 3s2 3p6 3d5 4s2
For the electrons of oxygen atom, which of the following statements is correct?
(i) Zeff for an electron in a 2s orbital is the same as Zeff for an electron in a 2p orbital.
(ii) An electron in the 2s orbital has the same energy as an electron in the 2p orbital.
(iii) Zeff for an electron in 1s orbital is the same as Zeff for an electron in a 2s orbital.
(iv) The two electrons present in the 2s orbital have spin quantum numbers ms but of opposite sign.
Ans: (iv) The two electrons present in the 2s orbital have spin quantum numbers ms but of opposite sign.
According to Pauli’s Exclusion Principle no two electrons should possess the same set of four quantum numbers.Thus the two electrons present in the 2s orbital have spin quantum numbers ms but of opposite sign.
If travelling at same speeds, which of the following matter waves have the shortest wavelength?
(i) Electron
(ii) Alpha particle (He2+)
(iii) Neutron
(iv) Proton
Ans: (ii) Alpha particle (He2+)
As the wavelength is inversely proportional to the mass of the particles thus the alpha particles would possess shortest wavelength among the above given option
$\lambda =\frac{\text{h}}{\text{mv}}$