I want to use a 10 point array to collect an answer with the addition of a don't know answer. So options would be:

Don't Know 1 2 3 4 5 6 7 8 9 10

Is this possible?

Use Array as the question type. When you're editing the responses add your choices (Don't Know, and then each number 1-10) to the settings when you click on the icon that looks like a grid with the top row colored in. (They will appear across the top of the question block then)