Question

Draw a Lewis electron-dot diagram for the cyclosilicate ion ${\mathbf{Si}}_6{{\mathbf{O}}_{18}}^{12-}$ which forms part of the structures of beryl and emerald.

Short answer

Cyclosilicate ion

Step-by-step solution

Lewis dot structure

The Lewis dot structure of a compound represents the structure of a molecule following the Lewis octet rule. The total number of valence electrons of all the atoms is counted and then arranged so that each atom attains eight electrons around it.

Explanation

The given compound is cyclosilicate ion.

Its symbol is ${\mathrm{Si}}_6{{\mathrm{O}}_{18}}^{12-}$ .

The total number of valence electrons in the ion is:

$\begin{array}{c}{\mathrm{n}}_{\mathrm{valence}\mathrm{electrons}}=[(4\times 6)+(6\times 18)+12]{\mathrm{e}}^{-}\\ =(24+108+12){\mathrm{e}}^{-}\\ =144{\mathrm{e}}^{-}\end{array}$

The Lewis dot structure consists of six silicon and six oxygen atoms in a ring each with single bonds.

Each Si-atom has two other oxygen atoms linked to it as side groups on the ring.

The Lewis dot structure is as shown below:

Cyclosilicate ion