Oxygen, symbolized as O, is a fundamental chemical element known for its role in respiration and combustion. The Periodic Table organizes all known elements by their atomic number and recurring chemical properties. This structure allows scientists to predict how an element will interact with others based on its precise placement.
Pinpointing Oxygen on the Periodic Table
Oxygen is found toward the upper-right side of the Periodic Table. It is the eighth element, meaning its nucleus contains eight protons, giving it an Atomic Number of 8.
Oxygen is located in the second horizontal row, Period 2, which indicates the atom has two main energy levels for its electrons. It is situated in the vertical column labeled Group 16. This group placement signifies that all elements in this column share the feature of having six valence electrons.
Defining the Chalcogen Family
The elements in Group 16, including oxygen, sulfur, selenium, tellurium, and polonium, are formally known as the Chalcogens. This name originates from Greek words meaning “ore-forming,” which is fitting since many metal ores are found as oxides or sulfides.
The shared feature of having six valence electrons dictates the collective chemical tendency of the entire family. To achieve a stable octet, Chalcogens seek to gain two electrons. This tendency makes the most common oxidation state for the group negative two (-2). Moving down the column, oxygen and sulfur are nonmetals, while polonium exhibits metallic characteristics. The larger elements further down the group can also exhibit positive oxidation states like +4 and +6, unlike oxygen.
How Oxygen’s Position Dictates Its Chemical Behavior
Oxygen’s position at the top of the Chalcogen family in Period 2 makes its chemical behavior unique. Being the smallest Chalcogen atom, it holds onto its electrons tightly, leading to high electronegativity. Oxygen’s electronegativity value of 3.44 is second only to fluorine among all elements.
This high electronegativity means oxygen is a powerful oxidizing agent, readily pulling electrons from nearly every other element to form compounds called oxides. Its configuration allows it to form strong covalent double bonds with itself, resulting in the common, stable diatomic molecule, O2. Oxygen also exists as the triatomic allotrope ozone, O3, which is a highly reactive gas. This ability to form strong double bonds is a practical outcome of its placement on the Periodic Table.