The commonality among all elements in period 7 is that they belong to the same period in the periodic table. Period 7 is the seventh row of the periodic table, and it includes elements from atomic number 87 (francium, Fr) to atomic number 118 (oganesson, Og).
All elements in period 7 have their outermost electrons located in the seventh energy level, also known as the valence shell. This means that they share a similar electron configuration pattern, with increasing numbers of electrons occupying the 7s, 6d, and 5f orbitals.
However, it's important to note that there are significant differences among the elements in period 7 regarding their physical and chemical properties due to variations in atomic structure and the number of valence electrons.