You must have never come in contact with an ASCII character code table before then...
Space is represented by : 32 040 20 00100000 (decimal, octal, hexadecimal, binary respectively)
Tab is represented by: 9 011 09 00001001
That is traditionally 'whitespace'. This may have different encodings using other systems (EBCDIC etc).
As for your /n 'newline' -- or better expressed as end of line, or EOL -
It all depends on what hardware/operating system you are running on when you write your text file to disk:
Linux and Unix (and numerous other related and unrelated OSs) use Line Feed to represent the EOL marker.
Windows/DOS use Carriage Return - Line Feed (2 characters) to represent the EOL marker.
Carriage Return is represented by: 13 015 0D 00001101
Linefeed which is represented by: 10 012 0A 00001010
If you are talking about regular expressions - then /n may not be considered whitespace -- because it can serve as a delimiter -- represented by $ character. This also translates to editors such as vi. In Fortran and Python, the EOL marker is significant because it represents the end of a statement...and there are was to 'escape' the EOL such that a single statement can extend beyond a single line. As such it is not considered 'whitespace' during compilation.
So really what is/is not whitespace comes down to a mix of operating system, tool/programming language and libraries (e.g. regex) used when parsing said text file.