The d block elements are the 40 elements contained in the four rows of ten columns (3-12) in the periodic table. As all the d block elements are metallic, the term d-block metals is synonymous. This set of d-block elements is also often identified as the transition metals, but sometimes the group 12 elements (zinc, cadmium, mercury) are excluded from the transition metals as the transition elements are defined as those with partly filled d or f shells in their compounds. Inclusion of the elements zinc, cadmium and mercury is necessary as some properties of the group 12 elements are appropriate logically to include with a discussion of transition metal chemistry.
The term transition element or transition metal appeared to derive from early studies of periodicity such as the Mendeleev periodic table of the elements. His horizontal table of the elements was an attempt to group the elements together so that the chemistry of elements might be explained and predicted. In this table there are eight groups labeled I-VIII with each subdivided into A and B subgroups. Mendeleev recognized that certain properties of elements in Group VIII are related to those of some of the elements in Group VII and those at the start of the next row Group I. In that sense, these elements might be described as possessing properties transitional from one row of the table to the next.
In the following questions, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage.
A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
B. Assertion and reason both are correct statements but reason is not correct explanation for assertion.
C. Assertion is correct statement but reason is wrong statement.
D. Assertion is wrong statement but reason is correct statement.
1.Assertion: Group 12 elements are not considered as transition metals.
Reason: Transition metals are those which have incompletely filled d shell in their compounds.
2.Assertion: All d block elements are metallic in nature.
Reason: The d –block elements belong to Group3 -12 of the periodic table.
3.Assertion : Group VII elements of Mendeleev periodic table are transition elements.
Reason: Group I –VIII in Mendleev periodic table is divided into two subgroups, A and B.
4.Assertion: Nickel is a transition element that belongs to group 10 and period 4 of the modern periodic table.
Reason: Electronic configuration of Nickel is [Ar]183d84s2
