EAN (Effective atomic number ) of platinum in `[Pt(NH_(3))_(6)]Cl_(4)` is 86. The atomic number of Pt is ___________.

Options

A. 78
B. 76
C. 54
D. 86

Answer

To find the atomic number of platinum (Pt) in the coordination compound \([Pt(NH_3)_6]Cl_4\), we can use the formula for Effective Atomic Number (EAN):

\[ \text{EAN} = Z - n + 2l \]

Where:
- \( Z \) = atomic number of the metal
- \( n \) = oxidation state of the metal
- \( l \) = number of ligands

Given:
- EAN = 86
- The ligands are 6 ammonia molecules, which are neutral ligands, so \( l = 6 \).

### Step 1: Determine the oxidation state of platinum (Pt)

The overall charge of the complex \([Pt(NH_3)_6]Cl_4\) is neutral, and the chloride ions \(Cl^-\) have a charge of -1 each. Since there are 4 chloride ions, their total charge is -4.

Let the oxidation state of platinum be \( x \). The equation for the charge balance can be written as:

\[ x + 6(0) - 4 = 0 \]

Where the charge of ammonia is 0. Thus:

\[ x - 4 = 0 \]
\[ x = +4 \]

So, the oxidation state of platinum is +4.

### Step 2: Substitute values into the EAN formula

Now we can substitute the values into the EAN formula:

\[ 86 = Z - 4 + 2(6) \]

### Step 3: Simplify the equation

Now simplify the equation:

\[ 86 = Z - 4 + 12 \]
\[ 86 = Z + 8 \]

### Step 4: Solve for Z (atomic number of platinum)

Now, isolate \( Z \):

\[ Z = 86 - 8 \]
\[ Z = 78 \]

### Conclusion

The atomic number of platinum (Pt) is **78**.

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