An element has the electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d¹⁰ 7p³. Which of the following statements about this element is correct?
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Correct answer
A. It is a main-group element in period 7.
Principle or equation
The periodic table is arranged by electron configurations. The element's highest principal quantum number is 7, and the last subshell filled is 7p, which is a p-block (main-group) element.
Why this answer is correct
The configuration ends at 7p³, so the element is in period 7 and group 15 (p-block). Main-group elements include s- and p-block. Transition metals have partially filled d subshells, but here the 6d subshell is full (6d¹⁰), and the last electron is in 7p. Lanthanides and actinides are f-block, but the f subshells are full.
Example
Bismuth (Bi) has [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³, a main-group element in period 6.
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