The heaviest element, in terms of atomic weight, is Oganesson (Og), element 118.
While the term "heaviest" can be interpreted in different ways, concerning elements, it most commonly refers to atomic weight (also known as relative atomic mass). Atomic weight is the average mass of an element's atoms. Oganesson, a synthetic and radioactive element, has the highest atomic number (118) and thus the highest atomic weight among all known elements.
It's important to distinguish between atomic weight and density. Density refers to mass per unit volume. In terms of density, elements like Osmium (Os) and Iridium (Ir) are among the densest. However, these are different properties.
Therefore, specifically addressing the question of which element is "heaviest" in terms of atomic weight, the answer is Oganesson.
