Calcium (atomic number 20) has electron configuration 1s2,2s2,2p6,3s2,3p6,4s2. the atomic number of scandium is 21. which orbital does the 21st electron enter? a. 3d b. 4p c. 4d d. 4f

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).

ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.