# Are coinage metals and zinc transition elements?

> Copper is in, zinc is out


## Objectives

- Show that the coinage metals (Cu, Ag, Au) are transition elements: $d^{10}$ in the atom, but $d^9$ or $d^8$ in the +2 or +3 state.
- Show that Zn, Cd and Hg are not: $d^{10}$ in the atom and in the +2 ion.
- Decide for a new element from its atom and ion configurations, and justify it.

## 1. Electronic configurations and oxidation states




## 2. Two complete 3d sublevels

Predict: which of them are transition elements?

- Neither: their atoms are $d^{10}$
- Both: they are in the d-block
- Zinc only
- Copper only ✓

Both atoms have a complete 3d. In $\ce{Cu^{2+}}$ the 3d becomes incomplete ($3d^9$), so copper is a transition element; in $\ce{Zn^{2+}}$ the 3d stays complete ($3d^{10}$), so zinc is not.

[ar-EG] الذرتين الـ 3d بتاعهم مكتمل. في الـ $\ce{Cu^{2+}}$ الـ 3d بيبقى incomplete ($3d^9$)، فالـ copper يبقى transition element؛ لكن في الـ $\ce{Zn^{2+}}$ الـ 3d بيفضل مكتمل ($3d^{10}$)، فالـ zinc لأ.
## 3. Strip copper

Copper's oxidation states are +1 and +2. Remove electrons and watch 3d. electrons lost Cu atom: $[\text{Ar}]\ 4s^1\ 3d^{10}$: d complete $\ce{Cu+}$: $[\text{Ar}]\ 3d^{10}$: d still complete $\ce{Cu^{2+}}$: $[\text{Ar}]\ 3d^9$: d incomplete Test 2 passed In $\ce{Cu^{2+}}$ the 3d sublevel is incomplete ($3d^9$). So copper passes the second test.


## 4. Coinage metals

Coinage metals Copper, silver and gold, in group IB. Book Exercise 1, p.10 In the atom, the d sublevel is completely filled ($d^{10}$) in all three. But in the oxidation state +2 or +3, d is partially filled ($d^9$ or $d^8$). So they are transition elements.


## 5. Strip zinc

Zinc's only oxidation state is +2. Remove its electrons and watch 3d. electrons lost Zn atom: $[\text{Ar}]\ 4s^2\ 3d^{10}$ one 4s electron gone $\ce{Zn^{2+}}$: $[\text{Ar}]\ 3d^{10}$ Book Exercise 2, p.11 $\ce{Zn^{2+}}$ is still $3d^{10}$. Zinc, cadmium ($5s^2\ 4d^{10}$) and mercury ($6s^2\ 5d^{10}$) are $d^{10}$ in the atom and in the +2 ion. So they are not transition elements.


## 6. Worked: gold; your turn: silver

Step 1: The gold atom $\ce{_{79}Au}$: … $6s^1\ 5d^{10}$: d complete Step 2: Gold in the +3 state $\ce{Au^{3+}}$: … $5d^8$: d incomplete Gold loses its 6s electron, then two 5d electrons. $5d^8$ is incomplete, so gold is a transition element. Your turn: silver in the +2 state [Kr] stands for krypton's 36 electrons, as [Ar] stands for argon's 18. $\ce{_{47}Ag}$: [Kr] $5s^1\ 4d^{10}$. $\ce{Ag^{2+}}$: [Kr] 4d___ . So silver ___ a transition element (type: is / is not).


## 7. New cases

Element X: atom [Kr] $4d^{10}$. In its +2 state: [Kr] $4d^8$. Is X a transition element?

- Yes: d is incomplete in its +2 state ✓
- No: it has no s electrons in the atom
- No: its atom is $d^{10}$

The atom of X is $4d^{10}$, but in the +2 state it is $4d^8$, an incomplete d sublevel, so X is a transition element (X is palladium).

[ar-EG] ذرة الـ X هي $4d^{10}$، لكن في الـ +2 state بتبقى $4d^8$، يعني d sublevel مش مكتمل، فالـ X يبقى transition element (الـ X ده هو الـ palladium).
## 8. Summary

Coinage metals (Cu, Ag, Au): $d^{10}$ in the atom, but $d^9$ or $d^8$ in the +2 or +3 state. They are transition elements. Zn, Cd, Hg: $d^{10}$ in the atom and in the +2 ion. They are not transition elements, though they sit in the d-block. Test the atom first, then its oxidation states. Test the atom, then the ion Give reasons: coinage metals are transition elements In the atom, the d sublevel is completely filled ($d^{10}$). In the oxidation state **(+2) or (+3)** it is partially filled ($d^9$) or ($d^8$). Back to the hook: can you explain why copper is a transition element but zinc is not?



Chapter: Transition Elements (https://yaani.ai/ar/learn/chemistry/chem-s3-en.ch1)
Source: https://yaani.ai/ar/lesson/chem-s3-en.lesson-te.definition-applied