<P> There is an approximate correspondence between this nomenclature of blocks, based on electronic configuration, and groupings of elements based on chemical properties . The s - block and p - block together are usually considered as the main - group elements, the d - block corresponds to the transition metals, and the f - block are the lanthanides and the actinides . However, not everyone agrees on the exact membership of each set of elements, so that for example the group 12 elements Zn, Cd and Hg are considered as main group by some scientists and transition metals by others, because they are chemically and physically more similar to the p - block elements than the other d - block elements . Furthermore, the group 3 elements and the f - block are sometimes also considered main group elements due to their similarities to the s - block elements . Groups (columns) in the f - block (between groups 3 and 4) are not numbered . </P> <P> Helium is coloured differently from the p - block elements surrounding it because it is in the s - block, with its outer (and only) electrons in the 1s atomic orbital, although its chemical properties are more similar to the p - block noble gases due to its full shell . In addition to the blocks listed in this table, there is a hypothetical g - block which is not pictured here . The g - block elements can be seen in the expanded extended periodic table . Also, lanthanum and actinium are placed under scandium and yttrium to reflect their status as d - block elements, as they have no electrons in the 4f and 5f orbitals, respectively, while lutetium and lawrencium do . </P> <Table> <Tr> <Th_colspan="20"> hide <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> Blocks in the periodic table </Th> </Tr> <Tr> <Th> Group → </Th> <Th> </Th> <Th> </Th> <Th> </Th> <Th> </Th> <Th> </Th> <Th> 5 </Th> <Th> 6 </Th> <Th> 7 </Th> <Th> 8 </Th> <Th> 9 </Th> <Th> 10 </Th> <Th> 11 </Th> <Th> 12 </Th> <Th> 13 </Th> <Th> 14 </Th> <Th> 15 </Th> <Th> 16 </Th> <Th> 17 </Th> <Th> 18 </Th> </Tr> <Tr> <Th_colspan="3"> ↓ Period </Th> </Tr> <Tr> <Th> </Th> <Td> </Td> <Td_colspan="17"> </Td> <Td> He </Td> </Tr> <Tr> <Th> </Th> <Td> Li </Td> <Td> Be </Td> <Td_colspan="11"> </Td> <Td> 5 </Td> <Td> 6 </Td> <Td> 7 </Td> <Td> 8 O </Td> <Td> 9 </Td> <Td> 10 Ne </Td> </Tr> <Tr> <Th> </Th> <Td> 11 Na </Td> <Td> 12 Mg </Td> <Td_colspan="11"> </Td> <Td> 13 Al </Td> <Td> 14 Si </Td> <Td> 15 </Td> <Td> 16 </Td> <Td> 17 Cl </Td> <Td> 18 Ar </Td> </Tr> <Tr> <Th> </Th> <Td> 19 </Td> <Td> 20 Ca </Td> <Td> 21 Sc </Td> <Td> </Td> <Td> 22 Ti </Td> <Td> 23 V </Td> <Td> 24 Cr </Td> <Td> 25 Mn </Td> <Td> 26 Fe </Td> <Td> 27 Co </Td> <Td> 28 Ni </Td> <Td> 29 Cu </Td> <Td> 30 Zn </Td> <Td> 31 Ga </Td> <Td> 32 Ge </Td> <Td> 33 As </Td> <Td> 34 Se </Td> <Td> 35 Br </Td> <Td> 36 Kr </Td> </Tr> <Tr> <Th> 5 </Th> <Td> 37 Rb </Td> <Td> 38 Sr </Td> <Td> 39 Y </Td> <Td> </Td> <Td> 40 Zr </Td> <Td> 41 Nb </Td> <Td> 42 Mo </Td> <Td> 43 Tc </Td> <Td> 44 Ru </Td> <Td> 45 Rh </Td> <Td> 46 Pd </Td> <Td> 47 Ag </Td> <Td> 48 Cd </Td> <Td> 49 In </Td> <Td> 50 Sn </Td> <Td> 51 Sb </Td> <Td> 52 Te </Td> <Td> 53 </Td> <Td> 54 Xe </Td> </Tr> <Tr> <Th> 6 </Th> <Td> 55 Cs </Td> <Td> 56 Ba </Td> <Td> 57 La </Td> <Td> </Td> <Td> 72 Hf </Td> <Td> 73 Ta </Td> <Td> 74 </Td> <Td> 75 Re </Td> <Td> 76 Os </Td> <Td> 77 Ir </Td> <Td> 78 Pt </Td> <Td> 79 Au </Td> <Td> 80 Hg </Td> <Td> 81 Tl </Td> <Td> 82 Pb </Td> <Td> 83 Bi </Td> <Td> 84 Po </Td> <Td> 85 At </Td> <Td> 86 Rn </Td> </Tr> <Tr> <Th> 7 </Th> <Td> 87 Fr </Td> <Td> 88 Ra </Td> <Td> 89 Ac </Td> <Td> </Td> <Td> 104 Rf </Td> <Td> 105 Db </Td> <Td> 106 Sg </Td> <Td> 107 Bh </Td> <Td> 108 Hs </Td> <Td> 109 Mt </Td> <Td> 110 Ds </Td> <Td> 111 Rg </Td> <Td> 112 Cn </Td> <Td> 113 Nh </Td> <Td> 114 Fl </Td> <Td> 115 Mc </Td> <Td> 116 Lv </Td> <Td> 117 Ts </Td> <Td> 118 Og </Td> </Tr> <Tr> <Td_colspan="19"> </Td> </Tr> <Tr> <Td_colspan="5"> </Td> <Td> 58 Ce </Td> <Td> 59 Pr </Td> <Td> 60 Nd </Td> <Td> 61 Pm </Td> <Td> 62 Sm </Td> <Td> 63 Eu </Td> <Td> 64 Gd </Td> <Td> 65 Tb </Td> <Td> 66 Dy </Td> <Td> 67 Ho </Td> <Td> 68 Er </Td> <Td> 69 Tm </Td> <Td> 70 Yb </Td> <Td> 71 Lu </Td> </Tr> <Tr> <Td_colspan="5"> </Td> <Td> 90 Th </Td> <Td> 91 Pa </Td> <Td> 92 U </Td> <Td> 93 Np </Td> <Td> 94 Pu </Td> <Td> 95 Am </Td> <Td> 96 Cm </Td> <Td> 97 Bk </Td> <Td> 98 Cf </Td> <Td> 99 Es </Td> <Td> 100 Fm </Td> <Td> 101 Md </Td> <Td> 102 No </Td> <Td> 103 Lr </Td> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td_colspan="20"> <Table> <Tr> <Td> s - block </Td> <Td> p - block </Td> <Td> d - block </Td> <Td> f - block </Td> <Td> Background color shows the block of the periodic table </Td> </Tr> </Table> Primordial From decay Synthetic Border shows natural occurrence of the element </Td> </Tr> </Table> <Tr> <Th_colspan="20"> hide <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> Blocks in the periodic table </Th> </Tr>

What are the blocks of the periodic table