* Atomic number: The atomic number represents the number of protons in an atom's nucleus. It defines the element.

* Elements 27-31: These elements are located in the 4th row (period) of the periodic table.

Let's list the elements with atomic numbers between 27 and 31:

* 27: Cobalt (Co)

* 28: Nickel (Ni)

* 29: Copper (Cu)

* 30: Zinc (Zn)

* 31: Gallium (Ga)

So, any of these elements could be the answer.