Of the atoms listed below, which one will have at least one electron in its d orbital?

a. mg
b. k
c. s
d. cr
e. none of the above

D. Cr

Explanation:

In order to determine which atom has at least one electron in its d orbital, we have to write their theoretical electron configurations.

Cr has 4 electrons in d orbitals. Cr belongs to the d-block in the periodic table.

the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).

i think it's letter a.