Since we are talking about the 1s electron, the electron would spend most of the time close to the nucleus. To explain a 15 year old child we can take example of a merry-go-round, we can take a 360-degree camera and place it inside the merry-go-round on time lapse mode and spin around the merry-go-round. The camera captures sort of an halo of the person spinning the ride. This halo is similar to the electron cloud of 1s electron over time.