Find Subscript Value of Beryllium in Beryl Mineral Formula

To find the value of $n$ in the chemical formula of Beryl, $\text{Be}_n\text{Al}_2\text{Si}_6\text{O}_{18}$, we can use the principle of electrical neutrality, where the sum of oxidation numbers of all atoms in a neutral compound is equal to zero.

The oxidation states of the constituent elements in this silicate mineral are:

• Beryllium ($\text{Be}$): $+2$
• Aluminium ($\text{Al}$): $+3$
• Silicon ($\text{Si}$): $+4$
• Oxygen ($\text{O}$): $-2$

Setting up the charge neutrality equation for one formula unit:
$n(+2) + 2(+3) + 6(+4) + 18(-2) = 0$

Simplifying the equation:
$2n + 6 + 24 - 36 = 0$
$2n + 30 - 36 = 0$
$2n - 6 = 0$
$2n = 6$
$n = 3$

Thus, the value of $n$ is $3$.