Boron has two stable isotopes, `.^(10)B(19%)` and `.^(11)B(81%)`. The atomic mass that should appear for boron in the periodic table is

Options

A. 10.81
B. `10^(5)`
C. 11
D. 10.5

Answer

To find the atomic mass of boron that should appear in the periodic table, we will calculate the weighted average of its isotopes based on their abundance. Boron has two stable isotopes: \( ^{10}B \) with an abundance of 19% and \( ^{11}B \) with an abundance of 81%.

### Step-by-step Solution:

1. **Identify the isotopes and their abundances**:
- Isotope 1: \( ^{10}B \) with an atomic mass of 10 and an abundance of 19%.
- Isotope 2: \( ^{11}B \) with an atomic mass of 11 and an abundance of 81%.

2. **Convert the percentages to decimal form**:
- Abundance of \( ^{10}B \): \( \frac{19}{100} = 0.19 \)
- Abundance of \( ^{11}B \): \( \frac{81}{100} = 0.81 \)

3. **Use the formula for average atomic mass**:
\[ \text{Average Atomic Mass (AAM)} = ( \text{Abundance of } ^{10}B \times \text{Mass of } ^{10}B ) + ( \text{Abundance of } ^{11}B \times \text{Mass of } ^{11}B ) \]

4. **Substitute the values into the formula**:
\[ \text{AAM} = (0.19 \times 10) + (0.81 \times 11) \]

5. **Calculate each term**:
- For \( ^{10}B \): \( 0.19 \times 10 = 1.9 \)
- For \( ^{11}B \): \( 0.81 \times 11 = 8.91 \)

6. **Add the results together**:
\[ \text{AAM} = 1.9 + 8.91 = 10.81 \]

7. **Conclusion**:
The average atomic mass of boron that should appear in the periodic table is **10.81**.