Q: Can a chord contain 3 consecutive notes (say, C C# D) but voiced in a way that would make a proper chord and won't sound dissonant? For example, 2 consecutive notes like C# and D can be turned into a DMaj7 chord. (Extra notes may be added)
A: no. once you have 3 in a row you are decisively outside of 'nice town,' no matter how you slice it. whereas, like you said, just 2 can easily be made 'nice' if they are surrounded with nice harmony