Important Questions for CBSE Class 9 Science Chapter 2 Is Matter Around us Pure IMPORTANT QUESTIONS 1 MARK QUESTIONS Question.1. Define atomic number. How it is denoted ? Answer. Number of protons of an atom determines its atomic number. It is denoted by 'Z'. Question.2. What are nucleons ? Answer. Protons and neutrons present in the nucleus of an atom are called … [Read more...]