1. The problem asks for the composition of the nucleus of the isotope $^{26}_{12}\text{Mg}$. 2. The atomic number (bottom number) is 12, which represents the number of protons. 3. The mass number (top number) is 26, which is the total number of protons and neutrons. 4. To find the number of neutrons, subtract the number of protons from the mass number: $$\text{Neutrons} = 26 - 12 = 14$$ 5. The nucleus contains protons and neutrons only; electrons are outside the nucleus. 6. Therefore, the nucleus of $^{26}_{12}\text{Mg}$ has 12 protons and 14 neutrons. 7. Looking at the options, the correct composition is: Protons: 12 Neutrons: 14 Electrons: 0 (since electrons are not part of the nucleus) 8. This corresponds to option D. Final answer: D. 12 | 14 | 0