Use the periodic table to identify the element indicated by each electron configuration by typing in the chemical symbol for the element. 1s22s22p6: 1s22s22p63s23p3: 1s22s22p63s23p64s1: 1s22s22p63s23p64s23d8: 1s22s22p63s23p64s23d104p65s24d3:

To determine what elements are represented by the electron configuration given above, we need to know the sum of the exponents of each term or subshell involved in the configuration as this represent the atomic number of the element.

                                                                 Atomic Number          Element
1s2 2s2 2p6:                                      2 + 2 + 6 = 10                         neon
1s2 2s2 2p6 3s2 3p3:            2 + 2 + 6 + 2 + 3 = 15                  phosphorus
1s2 2s2 2p6 3s2 3p6 4s1: 2 + 2 + 6 + 2 + 6+1 = 19                    potassium
1s2 2s2 2p6 3s2 3p6 4s2 3d8:              20 + 8 =  28                    nickel
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d3:  30 + 6 + 2 +3 = 41                    niobium

Ican't see the chart but the density of both nickel and cobalt is 8.90 g/cm3, so it would be one of those.