With minimal editing to your code (Not sure if they've taught classes or not in your course), change:
def close_window(root):
root.destroy()
to
def close_window():
window.destroy()
and it should work.
Explanation:
Your version of close_window is defined to expect a single argument, namely root. Subsequently, any calls to your version of close_window need to have that argument, or Python will give you a run-time error.
When you created a Button, you told the button to run close_window when it is clicked. However, the source code for Button widget is something like:
# class constructor
def __init__(self, some_args, command, more_args):
#...
self.command = command
#...
# this method is called when the user clicks the button
def clicked(self):
#...
self.command() # Button calls your function with no arguments.
#...
As my code states, the Button class will call your function with no arguments. However your function is expecting an argument. Thus you had an error. So, if we take out that argument, so that the function call will execute inside the Button class, we're left with:
def close_window():
root.destroy()
That's not right, though, either, because root is never assigned a value. It would be like typing in print(x) when you haven't defined x, yet.
Looking at your code, I figured you wanted to call destroy on window, so I changed root to window.