The d- and f-Block Elements

Chemistry · Class 12

Simulation · Chemistry · Class 12

Which electrons leave first when a 3d atom forms an ion?

From the lesson Position and electronic configuration in The d- and f-Block Elements. Change the values and watch what happens.

Which electrons leave first when a 3d atom forms an ion?Chemistry · Class 12

The idea behind it

NCERT §4.1; §4.2

  • The d-block is groups 3 to 12, where the d orbitals of the second-outermost shell fill. The f-block is the separate two-row panel at the foot of the table, where 4f and 5f orbitals fill. The elements are called transition and inner transition metals.
  • Four transition series: 3d (Sc to Zn), 4d (Y to Cd), 5d (La, then Hf to Hg) and 6d (Ac, then Rf to Cn). The 4f series (Ce to Lu) are the lanthanoids and the 5f series (Th to Lr) the actinoids.
  • IUPAC definition: a transition metal has an incomplete d subshell in the neutral atom or in its ions. Zn, Cd and Hg keep a full d¹⁰ set in the ground state and in their usual oxidation states, so they are not transition metals, though they are studied with them as the last members of each series.
  • Outer configuration in general: (n−1)d¹⁻¹⁰ ns¹⁻². Palladium is the exception to the ns part: 4d¹⁰ 5s⁰.
  • Because the (n−1)d and ns levels are so close in energy, half-filled and filled d sets win: Cr is 3d⁵ 4s¹ (not 3d⁴ 4s²) and Cu is 3d¹⁰ 4s¹ (not 3d⁹ 4s²).
  • Zn, Cd, Hg and Cn share the configuration (n−1)d¹⁰ ns².
  • Scandium (3d¹ 4s²) counts as a transition element because its atom has an incomplete 3d set; zinc does not, because it is d¹⁰ both as an atom and as Zn²⁺. Silver is 4d¹⁰ 5s¹ as an atom, but in the +2 state it is 4d⁹, so it is a transition element.
  • d orbitals reach further out towards the edge of the atom than s and p orbitals, so they feel the surroundings more and affect neighbouring atoms. Partly filled d orbitals lead to variable oxidation states, coloured ions, complex formation, catalytic activity and paramagnetism.
  • Elements along a transition row resemble one another more closely than the members of a main-group period do, though some group similarities exist too.