Question

If $\text{Ne}$ and $\text{B}$ have 10 and 6 neutrons respectively, what are their mass numbers?

• A. $\text{Ne}$ - 20
  $\text{B}$ - 13
• B. $\text{Ne}$ - 21
  $\text{B}$ - 12
• C. $\text{Ne}$ - 20
  $\text{B}$ - 11
• D. $\text{Ne}$ - 21
  $\text{B}$ - 13

Answer 1

The correct option is C $\text{Ne}$ - 20

$\text{B}$ - 11

Neon (Ne):
Atomic number of neon= 10
Therefore,
Number of protons= Number of neutrons= 10
Mass number = Number of protons + Number of neutrons
$\Rightarrow$ Mass number= 10+ 10= 20

Boron (B):
Atomic number of boron = 5
Therefore,
Number of protons= Number of electrons= 5
But number of neutrons= 6
Mass number= Number of protons + Number of neutrons
$\Rightarrow$ Mass number = 5 + 6= 11