Question

Write the chemical formula for the covalent compounds and mention the molecular weight after the formula

Silicon dioxide.

Answer 1

Covalent compound

• Covalent compounds are compounds having strong intramolecular bonds. atoms within the compound are tightly held together
• A covalent bond is formed by sharing of electron pairs between atoms. these electron pairs are known as shared pairs or bonding pairs.

Silicon dioxide

• Silicon dioxide contains one silicon atom and ‘di’ means 2, so two oxygen atoms are present in the molecule
• silicon has a valency of +4 and oxygen has a valency of -2

$$\begin{gathered} \mathrm{Si}\mathrm{O} \\ 42(\mathrm{crossmultiply}\mathrm{the}\mathrm{valencies}\mathrm{as}\mathrm{their}\mathrm{subscripts}) \\ {\mathrm{Si}}_2{\mathrm{O}}_4(\mathrm{simplifying}\mathrm{the}\mathrm{ratio}\mathrm{of}\mathrm{atoms}) \\ {\mathrm{SiO}}_2 \end{gathered}$$

• The chemical formula for silicon dioxide is ${\mathbf{SiO}}_{\mathbf{2}}$

Molecular weight

• Mass of Si - 28
• Mass of O - 16
• Molecular weight of ${\mathrm{SiO}}_2$ = 28 + (2 x 16) = 60 g