Final answer:
Excessive penetration in welding is when the weld root penetrates deeper than specified, not to be confused with electronic penetration in atomic physics.
Step-by-step explanation:
The term excessive penetration in the context of welding refers to the condition where the root penetration of a weld is deeper than what is specified by the design requirements. In other words, it means that the weld metal penetrates too far into the base metal, potentially leading to defects in the weld's quality and performance. This contrasts with the concept of penetration in atomic physics, which describes the ability of electrons in an orbital to get closer to an atomic nucleus.