미해결 질문Which of these refers to atoms with the same atomic number but different atomic masses?1723views
미해결 질문The atomic number of fluorine is 9 and its atomic mass is 19. How many neutrons does fluorine have?1541views
미해결 질문One isotope of sodium has 11 protons and 7 neutrons. What is the mass number of this isotope?1718views
미해결 질문How many protons, neutrons, and electrons are there in a neutral atom of 131I (iodine-131)?1542views