Articles > Quizzes & Surveys > Hydrogen definition – quiz Hydrogen definition – quiz Quiz Choose the best answer. 1. Which of the following is true about hydrogen? Chemical symbol is H2O The heaviest element Atomic number of 1 2. Forms when the hydrogen atom loses or gains an electron Hydrogen isotope Hydrogen ion Hydrogen allotrope 3. Diatomic hydrogen Hydrogen isotope Hydrogen ion Hydrogen allotrope 4. Produces proton gradient Hydrogen isotope Hydrogen ion Hydrogen allotrope 5. Chemical bond between water molecules Hydrogen bond Covalent bond Ionic bond Send Your Results (Optional) Your Name To Email Time is Up!