When an element in the periodic table has a high ionization potential, what is the most likely underlying cause for this characteristic?

A high ionization potential means that removing an electron is very difficult, which happens when the outer electron is tightly bound to the nucleus. This tight binding usually occurs because the electron is in a filled or nearly filled valence shell, giving the atom a very stable, low‑energy configuration. The attraction is stronger when the effective nuclear charge is high, as the nucleus pulls the electron in more forcefully. For example, neon has a full 2p shell and a strong nuclear pull, so its first ionization energy is one of the highest among the elements. Thus, the most likely cause of a high ionization potential is a stable, closed‑shell electron arrangement that strongly holds onto its electrons.