Question

Using the mass spectrum provided below:
Determine the relative atomic mass and identify the element.

• A. $Be,9.0122amu$
• B. $B,10.199amu$
• C. $C,12.011amu$
• D. $N,14.007$

Answer 1

Answer: (B)

$B,10.199amu$

The relative atomic mass

$=\frac{[{\text{atomic mass of}}^{10}X\times {\text{abundance of}}^{10}X]+[{\text{atomic mass of}}^{11}X\times {\text{abundance of}}^{11}X]}{{\text{abundance of}}^{10}X+{\text{abundance of}}^{11}X}=\frac{[\text{10}\times \text{80.1}]+[\text{11}\times \text{19.9}]}{\text{80.1}+\text{19.9}}=\text{10.199 amu}$

10.199 is close to atomic mass of B which is 10.8. Hence, our element is boron.