Chemistry is different from physics in that its focus has historically been on understanding what gives rise to the variation of matter, rather than asking "what is matter", which is one of the more profound questions physics asks. By extension chemistry also concerns itself with how matter can be transformed within this manifold of possible forms.
Chemistry is an extremely broad field that encompasses just about anything you can think of, as reflected in the great variety of subfields with hyphenated or compound names: geochemistry, astrochemistry, biochemistry, physical chemistry (not to be confused with chemical physics), nuclear chemistry, analytical chemistry, inorganic chemistry, organometallic chemistry, organic chemistry, chemical engineering, petrochemistry, agrochemistry, food chemistry, quantum chemistry, electrochemistry, among many others and including only those that include "chemistry" in their name (unlike say molecular biology, protein science, materials science and many other fields which are arguably also chemical sciences, or contain a strong chemical component).
This is why chemists proudly state that chemistry is the central science.
For more information on the great scope of chemistry you may want to check what branches exist within a professional society such as the ACS (American Chemical Society).
Addendum: Given the question "what are the central principles found throughout chemistry", emphasizing the role of the electrons makes sense, since describing their behavior is a key concern for understanding the structure and reactivity of compounds. But I'd say the fundamental principles are "quantum mechanics" and the "principle of charge" (the latter given as an answer elsewhere) and not restrict myself to the electron.