미해결 질문Which of these refers to atoms with the same atomic number but different atomic masses?1727views
미해결 질문The atomic number of fluorine is 9 and its atomic mass is 19. How many neutrons does fluorine have?1547views
미해결 질문One isotope of sodium has 11 protons and 7 neutrons. What is the mass number of this isotope?1721views