Chemistry · Periodic Classification Of Properties · NEET
Palladium has Z = 46. Its actual ground-state configuration is [Kr] 4d¹⁰ 5s⁰. Written in full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s⁰. Notice the 5s orbital is completely empty and the 4d orbital is completely full with 10 electrons. This is why Pd is called the 'anomaly' of the d-block.
The normal d-block rule is (n-1)d^(1-10) ns^(0-2). Filling by the usual order for 46 electrons would give [Kr] 4d⁸ 5s² (that is 8 electrons in 4d and 2 in 5s). But the real Pd atom does NOT do this. Both 5s electrons shift into 4d, giving 4d¹⁰ 5s⁰. So the expected 4d⁸ 5s² is wrong, and the actual is 4d¹⁰ 5s⁰.
Two reasons work together. First, in the 4d/5s region the energy gap between the 4d and 5s orbitals is very small, so an electron can move between them easily. Second, a completely filled set of orbitals (here 4d¹⁰) is extra stable. So both 5s electrons drop into 4d to reach the stable, fully-filled 4d¹⁰ arrangement. The energy you save by making 4d full is more than the cost of emptying 5s.
Cr and Cu keep ONE s-electron: Cr is 3d⁵ 4s¹ (half-filled d) and Cu is 3d¹⁰ 4s¹ (full d, but still one 4s electron). Palladium is more extreme — it removes BOTH s-electrons and has ZERO in 5s (4d¹⁰ 5s⁰). So Pd is the only common example where the outer s-shell is completely empty in the ground state.
Yes. Palladium is in Group 10, period 5, and it is a genuine d-block metal. It shows the usual d-block behaviour: it is a metal, forms coloured compounds, shows variable oxidation states, and is a famous catalyst (used in hydrogenation and car catalytic converters). The empty 5s just makes its written configuration unusual; it does not remove it from the d-block.
Yes. The NCERT Chemistry text (classification of elements section) gives the d-block general configuration as (n-1)d^(1-10) ns^(0-2) and then adds the exact phrase 'except for Pd where its electronic configuration is 4d¹⁰ 5s⁰'. NEET questions on d-block configuration expect you to remember this single named exception, so it is worth memorising.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Palladium has atomic number Z = 46. So a neutral Pd atom has 46 electrons arranged as [Kr] 4d¹⁰ 5s⁰.
Palladium (Pd) is the named exception in NCERT. Its outer configuration is 4d¹⁰ 5s⁰ instead of the expected 4d⁸ 5s², making it the only d-block element with a completely empty outermost s-orbital.
Because a completely filled 4d¹⁰ set has extra stability, and the 4d–5s energy gap is very small in this region. So both 5s electrons move to 4d, and the atom reaches a lower, more stable energy.
When Pd forms ions like Pd²⁺, it loses 4d electrons (since 5s is already empty), giving Pd²⁺ = [Kr] 4d⁸. This is normal for d-block ions, which lose ns electrons first and then (n-1)d electrons — but Pd simply has no ns electrons to begin with.
Palladium is a metal. It is a shiny, silvery-white transition metal used mainly as a catalyst, for example in car exhaust converters and in hydrogenation reactions.
