Main group elements prior to the appearance of the transition group elements in the periodic chart (ie, elements number 1 through 20) have no electrons in d atomic orbitals, but only in their s and p orbitals. (Though the low-lying, but empty d orbitals are thought to play a role in third-period elements such as silicon, phosphorus and sulfur)
/ Sc 21 Y 39 Lu 71 Lr 103 3 (IIIB) | Ti 22 Zr 40 Hf 72 Unq 104 4 (IVB) | V 23 Nb 41 Ta 73 Unp 105 5 (VB) | Cr 24 Mo 42 W 74 Unh 106 6 (VIB) transition metal / Mn 25 Tc 43 Re 75 Uns 107 7 (VIIB) \ Fe 26 Ru 44 Os 76 Uno 108 8 (VIIIB) | Co 27 Rh 45 Ir 77 Une 109 9 (VIIIB) | Ni 28 Pd 46 Pt 78 10 (VIIIB) | Cu 29 Ag 47 Au 79 11 (IB) \ Zn 30 Cd 48 Hg 80 12 (IIB)