The d- and f-Block Elements

Chemistry · Class 12

Simulation · Chemistry · Class 12

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

"Which electrons leave first when a 3d atom forms an ion?" is a free, interactive Class 12 Chemistry simulation for NEET and JEE, built on the NCERT section "Position and electronic configuration" in The d- and f-Block Elements. Orbital boxes for 4s and 3d of Sc–Zn: build the atom (with Cr and Cu anomalies), then remove electrons one at a time, 4s first, to make M⁺, M²⁺, M³⁺. NEET has asked about this idea 3 times in 10 years of papers. JEE Main asked 61 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).

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

What it shows

NCERT §4.1; §4.2; §4.3.3

Orbital boxes for 4s and 3d of Sc–Zn: build the atom (with Cr and Cu anomalies), then remove electrons one at a time, 4s first, to make M⁺, M²⁺, M³⁺.

Controls

3 to try

  • Sliderelement Sc–Zn
  • Buttonremove one electron (user chooses 4s or 3d box; wrong order flagged)
  • Readoutsconfiguration, unpaired electrons, transition element? (incomplete d in atom or ion)

Try this

Build Fe³⁺ from Fe by removing electrons in the right order to reach [Ar]3d⁵, then show why Zn²⁺ is not a transition-metal ion.

Common mistake

Removing 3d electrons before 4s / calling Zn a transition element.

In NEET

10 years of papers

Asked 3 times in 10 years of NEET.

See the past questions: Quantum Numbers, The d- and f-Block Elements (chapter)

In JEE Main

42 shifts analysed

61 questions from The d- and f-Block Elements across the 42 JEE Main shifts Lumi has analysed (2017–2026).

See the past questions

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.

Questions

5 answers

What does the "Which electrons leave first when a 3d atom forms an ion?" simulation show?
Orbital boxes for 4s and 3d of Sc–Zn: build the atom (with Cr and Cu anomalies), then remove electrons one at a time, 4s first, to make M⁺, M²⁺, M³⁺.
What mistake does the "Which electrons leave first when a 3d atom forms an ion?" simulation fix?
A common mistake it clears up: removing 3d electrons before 4s / calling Zn a transition element.
Has NEET asked about this idea?
Yes. NEET has asked about this idea 3 times in 10 years of papers.
Does JEE Main ask questions from The d- and f-Block Elements?
Yes. JEE Main asked 61 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
Is this simulation free?
Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Position and electronic configuration" in The d- and f-Block Elements (Class 12 Chemistry).

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