Climactic or Climatic?

I was a little confused over the spelling of the adjective that describes a story's climax (noun). Should it be "climactic" with an extra "c" inside or "climatic" without the "c"? Thankfully, Google came to the rescue.

So, I'm finally down to the last two chapters of my sci-fi novel. Of course, I tried my best to keep readers hooked on the storyline by bringing the narrative through a number of "dramatic" highs. But as every story reader would expect, there should be one "ultimate" sort of "climactic" finale near the end of the novel. 

The question is: Should the "climax" be in the last chapter, or is it better to be in the second last? I'd figured that most fiction novels usually preferred the latter, so that the ending chapter is used as a kind of housekeeping debrief for the story and its characters and, if circumstances permit, to create an abrupt ending that makes way for a sequel.

Now that I got the spelling and the order of the story ending sorted out, it's time to get into the grind to produce the finale "climax" readers are anticipating...