1. What is a node and what is its function
A node functions by connecting to others to relay and validate various data (transaction data, block data) to others. They validate blocks and transactions in its entirety. By running a node, you can relay these data and validate them for yourself.
2. Is the node a protective counter measure to protect the blockchain from scammers
No. A node doesn't serve those sorts of functions.
3.if the nodes act as a validator does this protection still extends to exchanges and why are they being hacked, cause I know that bitcoin is actually stored on a location in the blockchain and if it's anti bodies are nodes, how do some exchanges still get hacked ?
No. Exchanges are completely different and they can handle Bitcoin through their service but it is completely different from the protocol.
It appears that you have fundamental misunderstanding about how Bitcoin works. You should search for resources online and understand them before asking any questions, or else none of the discussions would be productive. Here's a site for starters:
https://learnmeabitcoin.com/.