Final answer:
The atom with 82 protons, 82 electrons, and 126 neutrons is represented by the chemical symbol ²82Pb¹208, which is the isotope of lead (Pb) with a mass number of 208.
Step-by-step explanation:
The complete chemical symbol for the atom containing 82 protons, 82 electrons, and 126 neutrons is 208Pb. The element with 82 protons is lead (Pb). To write the complete symbol, you use the atomic number (number of protons) as a subscript and the mass number (sum of protons and neutrons) as a superscript. The mass number is calculated as 82 protons + 126 neutrons = 208. Therefore, the complete chemical symbol is ²82Pb¹208.