This set of Class 12 Chemistry Chapter 8 Multiple Choice Questions & Answers (MCQs) focuses on “Electronic Configurations of the D-Block Elements”.
1. Which of the following are d-block elements, but not regarded as transition elements?
a) Ru, Ag, Au
b) Zn, Ru, Pd
c) Zn, Cd, Hg
d) Cd, Rh, Pd
View Answer
Explanation: Transition elements refer to those d-block elements who have their penultimate shells incomplete. In the case of Zinc, cadmium and mercury, since their penultimate shell is completely occupied, they are referred to as d-block elements and not regarded as transition elements.
2. Why do transition elements form alloys so easily?
a) Atomic size
b) Orbital configuration
c) Very light
d) Hard elements
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Explanation: Alloys are combinations of metals or elements in the form of a compound or a solution. Transition elements are highly capable in forming alloys because they have similar atomic size and can substitute each of their positions in a crystal lattice.
3. Which of the following has the highest atomic number?
a) Scandium
b) Titanium
c) Cadmium
d) Lanthanum
View Answer
Explanation: In the periodic table, when you move down the group, the atomic number increases. In the given options, scandium and titanium belong to the 3d series, cadmium belongs to the 4d series and Lanthanum belongs to the 5d series. Therefore, Lanthanum will have the highest atomic number.
4. What is the oxidation state exhibited by actinium?
a) +4
b) +1
c) +2
d) +3
View Answer
Explanation: Actinium is the first member of the actinoid series. Its atomic number is 89. The electronic configuration of actinium is [Rn]6d17s2. It has only three electrons to lose. Therefore, actinium is generally only found in the +3-oxidation state.
5. Where does the last electron of d-block element go?
a) nd
b) (n-1)d
c) np
d) (n-1)s
View Answer
Explanation: In these elements, the last electron enters the d orbital of the penultimate shell, i.e., the last electron goes to (n-1) d orbital. Hence, these elements are named as d-block elements. These elements have partly filled d-subshells in their elementary form or in their simple ions.
6. Why does Zinc not show variable valency?
a) Complete ‘d’ subshell
b) Inert pair effect
c) 4s2 subshell
d) 4s3 subshell
View Answer
Explanation: Both zinc and mercury have completely filled d-orbital. So, they tend to lose only 2 electrons from their outermost shell and have only one oxidation state. Hence, they only show a valency of +2 and do not show variable valency.
7. What is the common oxidation state of scandium? (At. No. of Sc = 21)
a) +4
b) +3
c) +1
d) +5
View Answer
Explanation: The properties of scandium compounds are intermediate between those of aluminium and yttrium. A diagonal relationship exists between the behaviour of magnesium and scandium, just as there is between beryllium and aluminium. In the chemical compounds of the elements in group 3, the predominant oxidation state is +3.
8. Among d-block elements, the most abundant element belongs to the first transition state.
a) True
b) False
View Answer
Explanation: Iron and titanium are the most abundantly found transition elements. The most abundant transition metal in Earth’s solid crust is iron, which is fourth among all elements and second (to aluminum) among metals in crustal abundance.
9. Which of the following statement is correct?
a) The properties of various actinoids are very similar
b) 4f and 5f orbitals are equally shielded
c) D-block elements show irregular and erratic chemical properties
d) 4d and 5d orbitals are equally shielded
View Answer
Explanation: There is very little variance in the atomic size of the actinoids and so, they show similar properties. 4f and 5f orbitals belong to different energy levels and so are unequally shielded. The same applies to the 4d and 5d orbitals. The d-block elements are known to show irregular and erratic chemical properties.
10. The main factor for the cause of lanthanide contraction is poorer shielding of 5d electrons by 4f electrons.
a) True
b) False
View Answer
Explanation: Lanthanide contraction is the steady decrease in the size of the atoms with increasing atomic number from lanthanum (atomic number 57) through lutetium (atomic number 71). The Lanthanide Contraction is caused by a poor shielding effect of the 4f electrons. It’s due to lanthanide contraction, as the atomic number increases, the size of the lanthanide atoms and their tripositive ions decreases.
Sanfoundry Global Education & Learning Series – Chemistry – Class 12.
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