Use these data: Ar ($Z = 18$, $39.95\ \text{u}$), K ($Z = 19$, $39.10\ \text{u}$), Te ($Z = 52$, $127.60\ \text{u}$), I ($Z = 53$, $126.90\ \text{u}$). A chemist arranges these four elements strictly in order of increasing atomic mass, with no correction for chemical properties. She fills the two slots after chlorine ($Z = 17$) and then the two slots after antimony ($Z = 51$). Which statement is correct?