How is a chemical bond formed? What is valence? What determines the structure of a molecule? These and many other questions regarding chemical bonding are answered by this brochure. The concept of valence is well known to every student, but, as it turns out, it is not at all so simple and often harbors a lot of unexpected and unusual things. A whole chapter is devoted to the issue of valency. The popularity of presenting such complex problems makes this brochure available to a wide range of readers. It is designed for high school students, students and all those who want to expand their knowledge of chemistry.