Good concept, but bad information.
Their facts and questions on the quizzes are wrong. By taking these quizzes, you will learn the wrong information. I am assuming that the programmer knows nothing about Chemistry, because there are facts that are completely wrong; for example the definition of an isotope according to this app is determined by the number of protons. A quick check on any chemistry site (or Chemistry book) will tell you that isotopes of a certain element are determined by the number of NEUTRONS of the atom. The concept of the app is very good, but for a CHEMISTRY app, it fails in basic CHEMISTRY.
