Question

Write chemical formulae for the following elements and compounds: hydrogen, zinc oxide, lead sulphide, iron, copper sulphate, calcium, water, calcium hydroxide, silver nitrate, carbon dioxide and mercury.

Answer 1

Chemical formula:

• chemical formula represents one molecule of an element or a compound.
• The chemical formula for an element is represented by the symbol of the element followed by its atomicity in subscript.
• For example the chemical formula of hydrogen is (${\mathrm{H}}_2$), iron is ($\mathrm{Fe}$), calcium is ($\mathrm{Ca}$), and mercury is ($\mathrm{Hg}$).
• The chemical formula for a compound is represented by the symbol of each element followed by the number of its atoms present in one molecule, written in the subscript.
• When the number of atoms of an element in the molecule is one, the subscript is not written.
• For example the chemical formula of water is (${\mathrm{H}}_2\mathrm{O}$ ), carbon dioxide (${\mathrm{CO}}_2$ ),zinc oxide is ($\mathrm{ZnO}$ ),lead sulphide($\mathrm{PbS}$),copper sulphate(${\mathrm{CuSO}}_4$),calcium hydroxide is ($\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$) and silver nitrate is (${\mathrm{AgNO}}_3$).