Periodic table (crystal structure)

For elements that are solid at standard temperature and pressure the table gives the crystalline structure of the most thermodynamically stable form(s) in those conditions. In all other cases the structure given is for the element at its melting point. Data is presented only for the elements that have been produced in bulk (the first 99, except for astatine and francium). Predictions are given for astatine, francium, and elements 100–114 and 118. No predictions are available for elements 115–117.

Table[]

v t Crystal structure of elements in the periodic table
1 H HEX																		2 He HCP
3 Li BCC	4 Be HCP												5 B RHO	6 C HEX	7 N HEX	8 O SC	9 F SC	10 Ne FCC
11 Na BCC	12 Mg HCP												13 Al FCC	14 Si DC	15 P ORTH	16 S ORTH	17 Cl ORTH	18 Ar FCC
19 K BCC	20 Ca FCC		21 Sc HCP	22 Ti HCP	23 V BCC	24 Cr BCC	25 Mn BCC	26 Fe BCC	27 Co HCP	28 Ni FCC	29 Cu FCC	30 Zn HCP	31 Ga ORTH	32 Ge DC	33 As RHO	34 Se HEX	35 Br ORTH	36 Kr FCC
37 Rb BCC	38 Sr FCC		39 Y HCP	40 Zr HCP	41 Nb BCC	42 Mo BCC	43 Tc HCP	44 Ru HCP	45 Rh FCC	46 Pd FCC	47 Ag FCC	48 Cd HCP	49 In TETR	50 Sn TETR	51 Sb RHO	52 Te HEX	53 I ORTH	54 Xe FCC
55 Cs BCC	56 Ba BCC		71 Lu HCP	72 Hf HCP	73 Ta BCC/TETR	74 W BCC	75 Re HCP	76 Os HCP	77 Ir FCC	78 Pt FCC	79 Au FCC	80 Hg RHO	81 Tl HCP	82 Pb FCC	83 Bi RHO	84 Po SC/RHO	85 At [FCC]	86 Rn FCC
87 Fr [BCC]	88 Ra BCC		103 Lr [HCP]	104 Rf [HCP]	105 Db [BCC]	106 Sg [BCC]	107 Bh [HCP]	108 Hs [HCP]	109 Mt [FCC]	110 Ds [BCC]	111 Rg [BCC]	112 Cn [HCP]	113 Nh [HCP]	114 Fl [FCC]	115 Mc	116 Lv	117 Ts	118 Og [FCC]
			57 La DHCP	58 Ce DHCP/FCC	59 Pr DHCP	60 Nd DHCP	61 Pm DHCP	62 Sm RHO	63 Eu BCC	64 Gd HCP	65 Tb HCP	66 Dy HCP	67 Ho HCP	68 Er HCP	69 Tm HCP	70 Yb FCC
			89 Ac FCC	90 Th FCC	91 Pa TETR	92 U ORTH	93 Np ORTH	94 Pu MON	95 Am DHCP	96 Cm DHCP	97 Bk DHCP	98 Cf DHCP	99 Es FCC	100 Fm [FCC]	101 Md [FCC]	102 No [FCC]

Legend:
…/… mixed structure
[…] predicted structure
BCC: body-centered cubic
FCC: face-centered cubic (cubic close packed)
HCP: hexagonal close packed
DHCP: double hexagonal close packed
ORTH: orthorhombic
TETR: tetragonal
RHO: rhombohedral
HEX: hexagonal
SC: simple cubic
DC: diamond cubic
MON: monoclinic
unknown or uncertain

Unusual structures[]

Usual crystal structures[]

Close packed metal structures[]

Many metals adopt close packed structures i.e. hexagonal close packed and face-centred cubic structures (cubic close packed). A simple model for both of these is to assume that the metal atoms are spherical and are packed together in the most efficient way (close packing or closest packing). In closest packing every atom has 12 equidistant nearest neighbours, and therefore a coordination number of 12. If the close packed structures are considered as being built of layers of spheres then the difference between hexagonal close packing and face-centred cubic is how each layer is positioned relative to others. Whilst there are many ways that can be envisaged for a regular buildup of layers:

• hexagonal close packing has alternate layers positioned directly above/below each other: A,B,A,B,... (also termed P6₃/mmc, Pearson symbol hP2, strukturbericht A3) .
• face-centered cubic has every third layer directly above/below each other: A,B,C,A,B,C,... (also termed cubic close packing, Fm3m, Pearson symbol cF4, strukturbericht A1) .
• double hexagonal close packing has layers directly above/below each other, A,B,A,C,A,B,A,C,.... of period length 4 like an alternative mixture of fcc and hcp packing (also termed P6₃/mmc, Pearson Symbol hP4, strukturbericht A3' ).^[8]
• α-Sm packing has a period of 9 layers A,B,A,B,C,B,C,A,C,.... (R3m, Pearson Symbol hR3, strukturbericht C19).^[9]

Hexagonal close packed[]

In the ideal hcp structure the unit cell axial ratio is ${\textstyle 2{\sqrt {\frac {2}{3}}}\sim 1.633}$. However, there are deviations from this in some metals where the unit cell is distorted in one direction but the structure still retains the hcp space group—remarkable all the elements have a ratio of lattice parameters c/a < 1.633 (best are Mg and Co and worst Be with c/a ~ 1.568). In others like Zn and Cd the deviations from the ideal change the symmetry of the structure and these have a lattice parameter ratio c/a > 1.85.

Face-centered cubic (cubic close packed)[]

More content relating to number of planes within structure and implications for glide/slide e.g. ductility.

Double hexagonal close packed[]

Similar to the ideal hcp structure, the perfect dhcp structure should have a lattice parameter ratio of ${\textstyle {\frac {c}{a}}=4{\sqrt {\frac {2}{3}}}\sim 3.267.}$ In the real dhcp structures of 5 lanthanides (including β-Ce) ${\textstyle c/2a}$ variates between 1.596 (Pm) and 1.6128 (Nd). For the four known actinides dhcp lattices the corresponding number vary between 1.620 (Bk) and 1.625 (Cf).^[10]

Body centred cubic[]

This is not a close packed structure. In this each metal atom is at the centre of a cube with 8 nearest neighbors, however the 6 atoms at the centres of the adjacent cubes are only approximately 15% further away so the coordination number can therefore be considered to be 14 when these are ong one 4 fold axe structure becomes face-centred cubic (cubic close packed).

See also[]

• Crystal structure

References[]

General

• P.A. Sterne; A. Gonis; A.A. Borovoi, eds. (July 1996). "Actinides and the Environment". Proc. of the NATO Advanced Study Institute on Actinides and the Environment. NATO ASI Series. Maleme, Crete, Greece: Kluver Academic Publishers. pp. 59–61. ISBN 0-7923-4968-7.
• L.R. Morss; Norman M. Edelstein; Jean Fuger, eds. (2007). The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Springer. ISBN 978-1402035555.

External links[]

• Strukturbericht Type A – structure reports for the pure elements
• Crystal Structures for the solid chemical elements at 1 bar