Q.Silver atom has completely filled d orbitals ($4d^{10}$) in its ground state. How can you say that it is a transition element?

Silver is classified as a transition element not by its ground-state configuration alone, but by the definition based on its ions.

Key idea: A transition element is defined as an element whose atom in the ground state or in any of its common oxidation states has an incomplete d subshell.

Reasoning:

1. In the ground state, silver has the configuration $[Kr]\,4d^{10}\,5s^1$ — the d subshell is completely filled.
2. However, silver commonly forms the $Ag^+$ ion by losing the single 5s electron. The configuration of $Ag^+$ is $[Kr]\,4d^{10}$, which is still completely filled. …

Why This Question Trips Students Up

The confusion is natural. You see $4d^{10}$ — a completely filled $d$ subshell — and think “that’s not a transition element.” But the official IUPAC definition (and the one used in Indian board exams) is broader:

This means we must check both the ground state and the common oxidation states of the element. Silver’s ground state is $4d^{10}5s^1$ — the $d$ subshell is full. But that’s not the end of the story.

Step-by-Step Reasoning

1. Write the ground-state electronic configuration of silver (Ag, atomic number 47).

   Following the Aufbau principle:

   $1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^2 4p^6 4d^{10} 5s^1$

   In condensed form: $[Kr]\,4d^{10}5s^1$.

   The $4d$ subshell is completely filled — no doubt about that.

2. Check the ground state against the definition.

   The ground state has $4d^{10}$ — a full $d$ subshell. So by the first part of the definition (incomplete $d$ subshell in the atom), silver does not qualify.

   But the definition has a second part: “or which can give rise to cations with an incomplete $d$ subshell.”

3. Examine the common oxidation states of silver.

   Silver most commonly forms $Ag^+$ (as in $AgNO_3$, $AgCl$, etc.).

   $Ag^+$: remove the $5s^1$ electron → configuration becomes $[Kr]\,4d^{10}$.

   That’s still a full $d^{10}$ — so $Ag^+$ does not have an incomplete $d$ subshell either.

   At this point, many students stop and conclude silver is not a transition element. But that’s a mistake — because we haven’t checked all common oxidation states.

4. Look for a less common but still important oxidation state: $Ag^{2+}$.

   Silver can also form $Ag^{2+}$ compounds (e.g., $AgF_2$, $AgO$). This is a stable oxidation state, though less common than $+1$.

   $Ag^{2+}$: remove the $5s^1$ electron and one $4d$ electron → configuration becomes $[Kr]\,4d^9$.

   $4d^9$ is incomplete — it has one vacancy in the $d$ subshell. …

Method: Electronic Configuration Analysis Based on IUPAC Definition

Step 1 – Recall the IUPAC definition of a transition element

A transition element is defined as an element whose atom has an incomplete d-subshell in its ground state or can form stable ions with an incomplete d-subshell.

Step 2 – Examine the ground state of silver

Silver (Ag, atomic number 47) has the ground state configuration:

Here, the $4d$ subshell is completely filled ($4d^{10}$). So in the ground state, silver does not have an incomplete d-subshell.

Step 3 – Check the ions formed by silver

Silver commonly forms the Ag⁺ ion by losing the single $5s$ electron:

The electronic configuration of Ag⁺ is:

This still has a completely filled $4d$ subshell — no incompleteness.

Step 4 – Check higher oxidation states

Silver can also form Ag²⁺ (e.g., in AgF₂). The configuration of Ag²⁺ is: …

Common Mistakes & How to Avoid Them

Mistake 1: Confusing "Completely Filled" with "Not a Transition Element"

The error: Students see $4d^{10}$ and immediately conclude silver cannot be a transition element because transition elements require incomplete d-orbitals.

Why it's wrong: The definition of a transition element (as per IUPAC and most Indian exam boards) is:

An element whose atom has an incomplete d-subshell either in its ground state or in any of its common oxidation states.

Silver's ground state is $[Kr]\,4d^{10}\,5s^1$. The $4d$ subshell is full — but in its common +1 oxidation state ($Ag^+$), the configuration becomes $[Kr]\,4d^{10}$ (still full). However, in the +2 oxidation state ($Ag^{2+}$), the configuration is $[Kr]\,4d^9$ — incomplete. That qualifies silver as a transition element.

How to avoid: Always check both the ground state and common oxidation states. Never judge solely from the ground state configuration.

Mistake 2: Forgetting to Check Oxidation States

The error: Students only look at the ground state and ignore the "or in any of its common oxidation states" part of the definition.

Why it's wrong: Many transition elements (like Cu, Ag, Au) have fully filled d-orbitals in the ground state but show incomplete d-orbitals in higher oxidation states.

How to avoid: Memorise the full definition word-for-word. When given a configuration, always ask: "Does this element form any common ion where the d-subshell becomes incomplete?"

Mistake 3: Misidentifying "Common Oxidation States"

The error: Students think $Ag^+$ (the most common oxidation state) has incomplete d-orbitals — it doesn't ($4d^{10}$). So they wrongly conclude silver is not a transition element.

Why it's wrong: The definition says any common oxidation state. For silver, $Ag^{2+}$ (though less common than $Ag^+$) is still a known oxidation state, and it has $4d^9$.

How to avoid: Know the common oxidation states of d-block elements:

• Silver: +1 (most common), +2 (less common but known)
• Copper: +1, +2 (both common)
• Zinc: +2 only — hence not a transition element

Mistake 4: Confusing "Transition Elements" with "d-Block Elements" …