Final answer:
Option C, O (Oxygen), S (Sulfur), Te (Tellurium), represents atoms with valence electrons in the same electron shell across different periods as they are all chalcogens in the same group of the periodic table.
Step-by-step explanation:
The question asks which set of symbols represents atoms with valence electrons in the same electron shell. Understanding the periodic table is crucial to answering this. Considering the periodic table, elements in the same group (vertical column) have the same number of valence electrons. Additionally, elements in the same period (horizontal row) have valence electrons in the same shell.
Option (C) O, S, Te are all chalcogens and are located in the same group (Group 16 or VI) of the periodic table. They each have six valence electrons, but more importantly for this question, their valence electrons are in the same shell relative to their periods.
For example, oxygen (O), being in the second period, has its valence electrons in the 2p shell, sulfur (S) in the third period has valence electrons in the 3p shell, and tellurium (Te) in the fifth period has valence electrons in the 5p shell. Therefore, option (C) O, S, Te represents atoms with valence electrons in the same electron shell relative to their respective periods on the periodic table.