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Practice each question, then open the answer or worked solution.
Identify the pairs which are not of isotopes?
(i) 12 6 X , 13 6Y
(ii) 35 17 X, 37 17Y
(iii) 146X, 147Y
(iv) 84X, 85Y
Ans: (iii) & (iv)
The isotopes are defined as atoms with identical atomic numbers but different mass numbers are known as isotopes.
Out of the following pairs of electrons, identify the pairs of electrons present in degenerate orbitals :
(i) (a) n = 3, l = 2, ml = –2, ms= − 1/2
(b) n = 3, l = 2, ml = –1, ms= − 1/2
(ii) (a) n = 3, l = 1, ml = 1, ms = + 1/2
(b) n = 3, l = 2, ml = 1, ms = + 1/2
(iii) (a) n = 4, l = 1, ml = 1, ms = + 1/2
(b) n = 3, l = 2, ml = 1, ms = + 1/2
(iv) (a) n = 3, l = 2, ml = +2, ms = − 1/2
(b) n = 3, l = 2, ml = +2, ms = + 1/2
Ans: (i)&(iv)
In a multielectron atomic system the energy of an electron depends not only on its principal quantum number (shell), but also on its azimuthal quantum number (subshell). Electrons having the same shells and same subshells have the same energy and they are known as degenerate orbitals.
Which of the following sets of quantum numbers are correct?
n | 1 | m1 | |
(i) | 1 | 1 | +2 |
(ii) | 2 | 1 | 1 |
(iii) | 3 | 2 | -2 |
(iv) | 3 | 4 | -2 |
Ans: (ii) & (iii)
For the given value of n (principal quantum number) the value of l (Azimuthal quantum number) varies from 0 to n-l.
However for the given value of l the ml(magnetic quantum number) varies from -l to +l
In which of the following pairs, the ions are iso-electronic?
(i) Na+, Mg2+
(ii) Al3+, O–
(iii) Na+ , O2–
(iv) N3–, Cl–
Ans: (i)&(iii)
Isoelectronic species are those species that possess the same number of electrons.
Here both Na+, Mg2+ possess 10 electrons and both Na+ , O2– possess 10 electrons.
Which of the following statements concerning the quantum numbers are correct?
(i) Angular quantum number determines the three dimensional shape of the orbital.
(ii) The principal quantum number determines the orientation and energy of the orbital.
(iii) Magnetic quantum number determines the size of the orbital.
(iv) Spin quantum number of an electron determines the orientation of the spin of electron relative to the chosen axis.
Ans: (i)&(iv)
a. Principal quantum number (n): It represents the size and energy of orbitals.
b. Azimuthal quantum number (l): It represents the subshell and shape of orbitals.
c. Magnetic quantum number (ml): It represents the orientation of the orbitals.
d. Spin quantum number (ms): It represents the direction of spin of electrons in the orbitals.