Fe2O3 + 3H2 → 2Fe + 3H2O There are
Fe (iron) atoms.

There are
O (oxygen) atoms.

There are
H (hydrogen) atoms
help asap

They are all in a iving organism.

Are you asking about a street map usage  if so here is your answer  a street map for a very limited area could simply be a bit map or a .jpg image.  but a more general map would probably store the streets as vectors.  but you shouldn't assume that there is one way to do it