Changing permissions recursively with chmod:

chmod -R 755 path_to_folder
Works

chmod --recursive 755 path_to_folder
Works

chmod -r 755 path_to_folder
DOES NOT WORK chmod: cannot access '755': No such file or directory

From man chmod:

The perm symbols represent the portions of the mode bits as follows:
r The read bits.

The op symbols represent the operation performed, as follows: - If no value is supplied for perm, the ``-'' operation has no effect. If no value is supplied for who, each permission bit specified in perm, for which the corresponding bit in the file mode creation mask is set, is cleared. Otherwise, the mode bits represented by the specified who and perm values are cleared.

Therefore -r tries to remove the read bits from directory 755, which obviously does not exist and therefore throws an error.