Which sequence is correct regarding the first ionisation potential of coinage metals ?

Options

A. `Cu gt Ag gt Au`
B. `Cu lt Ag lt Au`
C. `Cu gt Ag lt Au`
D. `Ag gt Cu gt Au`

Explanation

To determine the correct sequence regarding the first ionization potential of coinage metals (copper, silver, and gold), we need to analyze the trends in ionization potential based on their electronic configurations and periodic properties.

### Step-by-Step Solution:

1. **Identify the Coinage Metals**: The coinage metals are copper (Cu), silver (Ag), and gold (Au).

2. **Determine the Electronic Configurations**:
- Copper (Cu): [Ar] 3d^10 4s^1
- Silver (Ag): [Kr] 4d^10 5s^1
- Gold (Au): [Xe] 4f^14 5d^10 6s^1

3. **Understand the Trend in Ionization Potential**:
- Ionization potential generally decreases down a group in the periodic table due to increasing atomic size and shielding effect.
- However, when moving from one period to the next (like from Ag to Au), the presence of f-orbitals can affect the ionization potential due to poor shielding.

4. **Analyze the Size and Shielding Effects**:
- As we move from copper to silver, the atomic size increases, leading to a decrease in ionization potential. Thus, Cu has a higher ionization potential than Ag.
- When moving from silver to gold, the atomic size decreases because the 4f electrons (which are poorly shielding) increase the effective nuclear charge felt by the outermost electrons. Therefore, Au has a higher ionization potential than Ag.

5. **Establish the Order of Ionization Potentials**:
- From the above analysis, we can conclude:
- Cu > Ag (copper has a higher ionization potential than silver)
- Ag < Au (silver has a lower ionization potential than gold)
- Therefore, the correct order of first ionization potentials is:
- Cu > Au > Ag

6. **Final Conclusion**: The correct sequence regarding the first ionization potential of coinage metals is:
- **Copper (Cu) > Gold (Au) > Silver (Ag)**