In a novel, in a memoir, a good chapter is structured like a complete narrative: it begins with a situation, complications are introduced and build to a head, and…
And what?
Here’s where a chapter differs from a story. A chapter “ends” without a major resolution. The novel’s narrative arc continues on.
You might even say that lack of resolution is the hallmark of an effective chapter. The Cliff Hanger, for instance, is an extreme (and extremely successful) example of NOT achieving resolution. Where resolution would normally occur, a major new complication is introduced just as the chapter is winding down, compelling the reader to read on.
But since resolution isn’t the goal, there’s a common misconception that you are free to end a chapter anywhere you choose to cut it off–in other words, abandon structure altogether. But you can’t. Tripartite structure is too deeply ingrained in us: we need at least the illusion of dramatic closure to lend the chapter a closing beat.
What’s a closing beat? Almost anything–a thought, an event, a perception, a discovery. It can be as simple as your main character’s musings about tomorrow, as he goes to sleep, exhausted by the day’s events. Or it can a new and provocative piece of information, signaling to the reader that somewhere, somehow, a confrontation is looming.
Example: A husband reflects suddenly that his wife has lied to him about a trivial appointment that never actually existed. If we know the wife has been having an affair with his best friend, you can bet we’ll jump right into the next chapter: we sense something is going to happen, and we’re compelled to witness–and it’s mission accomplished: you’ve kept the reader onboard.
Overlook the need for a closing beat of some kind and you invite your readers to wonder: “That’s odd…why did it stop just there?” When a reader is thinking those thoughts, the story spell his been broken, and you’re losing valuable momentum.