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Actinides are the elements with atomic numbers from __________?

Correct answer: C. 89 to 103

  • A. 97 to 104
  • B. 101 to 115
  • C. 89 to 103
  • D. 36 to 43

Explanation

The actinide series is conventionally given as elements with atomic numbers 89 through 103, from actinium to lawrencium. These elements involve progressive filling of the 5f subshell, although some texts describe the inner f-block as beginning at thorium, atomic number 90. Option a is the likely mistake because it starts near the actinides but incorrectly ends at 104.

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About Electronic Structure of d-Block Elements

The electronic structure of d-block elements covers the filling of the (n-1)d and ns orbitals, general electronic configurations, and the exceptions shown by chromium and copper. It explains how partially filled d orbitals produce variable oxidation states, coloured ions, magnetic behaviour and complex formation, while distinguishing transition elements from elements with completely filled d subshells.

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