Question

1. calculate the relative atomic mass for nitrogen using the formula

$^{14}_{7}n = 99.63%$
$^{15}_{7}n = 0.37%$

1. calculate the relative atomic mass for boron using the following

$^{10}_{5}b = 19.90%$
$^{11}_{5}b = 80.10%$

Explanation:

Step1: Recall relative - atomic - mass formula

The relative atomic mass ($A_r$) of an element with isotopes is calculated as $A_r=\sum_{i} (m_i\times x_i)$, where $m_i$ is the mass number of the $i$-th isotope and $x_i$ is its relative abundance.

Step2: Calculate relative atomic mass of nitrogen

For nitrogen, $m_1 = 14$, $x_1=0.9963$ and $m_2 = 15$, $x_2 = 0.0037$.
$A_{r(N)}=14\times0.9963 + 15\times0.0037$
$=13.9482+0.0555$
$=14.0037$

Step3: Calculate relative atomic mass of boron

For boron, $m_1 = 10$, $x_1 = 0.1990$ and $m_2=11$, $x_2 = 0.8010$.
$A_{r(B)}=10\times0.1990+11\times0.8010$
$=1.99 + 8.811$
$=10.801$

Answer:

1. The relative atomic mass of nitrogen is $14.0037$.
2. The relative atomic mass of boron is $10.801$.