Write the atomic number of the element in which the filling of the 3d subshell just starts.
Answer: 21 (scandium).
Solution
The 3d subshell begins to fill after 4s is complete (at Ca, Z = 20).
The first element with a 3d electron is scandium: Z = 21, [Ar]3d4s.
The first element with a 3d electron is scandium: Z = 21, [Ar]3d4s.
CBSE Class 12 Board · 2002 · All India Compartment · Subjective