An element X has the electron configuration 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d1. Which block of the periodic table does this element belong to?
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Correct answer
C. d-block
Principle or equation
The block of an element is determined by the subshell that receives the last electron according to the Aufbau principle. Here the last electron enters the 6d subshell, so it is a d-block element.
Why this answer is correct
The configuration ends with 6d1, which is a d subshell. Therefore, the element is in the d-block. s-block elements have last electron in s, p-block in p, f-block in f.
Example
For example, the element with configuration [Rn] 5f14 6d1 7s2 is actinium (Ac), which is a d-block element.
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