My chihuahua just had one puppy?

Answer 1

This is called a singleton puppy. It is not unusual for a dog to give birth to one puppy, but it is uncommon. The average litter is about six puppies, but some dogs may have more or less.

Singleton puppies lack the companionship of literates, so they often grow up confused about their position in the "pack", may be over-playful because of the lack of playmates it had as a puppy and may be a little snappy because it didn't have siblings to test its "strength" on (which is a perfectly normal thing for puppies to do).
This behaviour is not the fault of the puppy. You can try to find a sibling for the singleton puppy by adopting a stray puppy.

Answer 2

It is possible for dogs to give birth to 1 puppy especially small breeds such as toy breeds. A group of puppies are called a litter and usually larger dogs give birth to more puppies in a litter rather than small Dog Breeds.

Answer 3

Chihuahua litters aren't that big. They are usually four puppies each litter. Its rare to have more.