How many structural isomers can you draw for pentane ?

Three structural isomers are possible for pentane.

$(i)$ $CH _{3}- CH _{2}- CH _{2}- CH _{2}- CH _{3}$

$(ii)$ $\begin{array}{*{20}{c}}
  {C{H_3} - C{H_2} - CH - C{H_3}} \\ 
  {\,\,\,\,\,\,\,\,\,\,\,\,|} \\ 
  {\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{H_3}\,\,} 
\end{array}$

$(iii)$ $\begin{array}{*{20}{c}}
  {\begin{array}{*{20}{c}}
  {\,C{H_3}} \\ 
  {|\,\,\,\,\,} 
\end{array}} \\ 
  {C{H_3} - CH - C{H_3}} \\ 
  {|\,\,\,\,\,\,} \\ 
  {\,\,C{H_3}} 
\end{array}$