An element X has the following isotopic composition:
`""^(200)X:90% ""^(199)X:8.0% ""^(202)X:2.0%`
The weight average atomic mass of the naturally occurring element X is closest to

Options

A. 201 amu
B. 202 amu
C. 199 amu
D. 200 amu

Explanation

To calculate the weight average atomic mass of the element X based on its isotopic composition, we will follow these steps:

### Step 1: Identify the isotopes and their abundances
- Isotope \(^{200}X\): 90%
- Isotope \(^{199}X\): 8%
- Isotope \(^{202}X\): 2%

### Step 2: Convert the percentages to decimal form
- \(^{200}X\): \(0.90\)
- \(^{199}X\): \(0.08\)
- \(^{202}X\): \(0.02\)

### Step 3: Multiply each isotope's atomic mass by its abundance
- For \(^{200}X\):
\[ 200 \times 0.90 = 180 \]
- For \(^{199}X\):
\[ 199 \times 0.08 = 15.92 \]
- For \(^{202}X\):
\[ 202 \times 0.02 = 4.04 \]

### Step 4: Sum the results from Step 3
\[ 180 + 15.92 + 4.04 = 199.96 \]

### Step 5: Round to the appropriate number of significant figures
The average atomic mass of element X is approximately \(200 \, \text{amu}\).

### Final Answer
The weight average atomic mass of the naturally occurring element X is closest to **200 amu**.

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