An unknown element has chemical behavior similar to that of silicon (si) and lead (pb). the unknown element has a mass greater than that of sulfur (s), but less than that of cadmium (cd). use the periodic table to determine the identity of the unknown element.

Ge ( Germanium)

Explanation:

The atomic mass of Ge is 72.61 and the atomic mass of S is 32.066 and the mass of Cd is 112.411 so being the only element in the same group as Si.

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.