The structures of metallic elements adopted at standard temperatures and pressures (STP) are color coded and shown below,[1] the only exception is mercury, Hg, which is a liquid and the structure refers to the low temperature form. The melting points of the metals (in K) is shown above the element symbol. Most of metallic elements are variations of the cubic crystal system, with the exceptions noted. Non-metallic elements, like the noble gases, are not crystalline solids at STP, while others, like carbon, may have several stable allotropes, so they are not listed.
Contents |
| bcc body centered cubic |
hcp hexagonal close packed |
fcc face centered cubic (cubic close packed) |
unusual structure | unknown / uncertain | nonmetal |
| H | He | |||||||||||||||||
| 453.69 Li bcc |
1560 Be hcp |
B | C | N | O | F | Ne | |||||||||||
| 370.87 Na bcc |
923 Mg hcp |
933.47 Al fcc |
Si | P | S | Cl | Ar | |||||||||||
| 336.53 K bcc |
1115 Ca fcc |
1814 Sc hcp |
1941 Ti hcp |
2183 V bcc |
2180 Cr bcc |
1519 Mn |
1811 Fe bcc |
1768 Co hcp |
1728 Ni fcc |
1357.8 Cu fcc |
692.68 Zn |
301.91 Ga |
Ge | As | Se | Br | Kr | |
| 312.46 Rb bcc |
1050 Sr fcc |
1799 Y hcp |
2128 Zr hcp |
2750 Nb bcc |
2896 Mo bcc |
2430 Tc hcp |
2607 Ru hcp |
2237 Rh fcc |
1828 Pd fcc |
1235 Ag fcc |
594 Cd |
430 In |
505 Sn |
904 Sb |
Te | I | Xe | |
| 302 Cs bcc |
1000 Ba bcc |
2506 Hf hcp |
3290 Ta bcc |
3422 W bcc |
3186 Re hcp |
3306 Os hcp |
2446 Ir fcc |
1768 Pt fcc |
1337.33 Au fcc |
234.32 Hg |
577 Tl hcp |
600.61 Pb fcc |
544.7 Bi |
Po | At | Rn | ||
| Fr | Ra bcc |
Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Uut | Uuq | Uup | Uuh | Uus | Uuo | ||
| ↓ | ||||||||||||||||||
| La |
Ce fcc |
Pr |
Nd |
Pm hcp |
Sm | Eu bcc |
Gd hcp |
Tb hcp |
Dy hcp |
Ho hcp |
Er hcp |
Tm hcp | Yb fcc |
Lu hcp | ||||
| Ac fcc |
Th fcc |
Pa | U | Np | Pu | Am hcp |
Cm hcp |
Bk | Cf | Es | Fm | Md | No | Lr | ||||
| Metal | structure family | coordination number | notes |
|---|---|---|---|
| Mn | cubic | distorted bcc - unit cell contains Mn atoms in 4 different environments [1] | |
| Zn | hexagonal | distorted from ideal hcp. 6 nearest neighbors in same plane- 6 in adjacent planes approx. 10% further away[1] | |
| Ga | orthorhombic | each Ga atom has one nearest neighbor at 244pm, 2 at 270pm, 2 at 273, 2 at 279pm.[1] | The structure is related to Iodine. |
| Cd | hexagonal | distorted from ideal hcp. 6 nearest neighbours in the same plane- 6 in adjacent planes approx. 10% further away[1] | |
| In | tetragonal | slightly distorted fcc structure[1] | |
| Sn | tetragonal | 4 at 302pm; 2 at 318pm; 4 at 377; 8 at 441pm [1] | |
| Sb | rhombohedral | puckered sheet; each Sb atom has 3 neighbours in the same sheet at 290.8pm; 3 in adjacent sheet at 335.5 pm.[1] | grey metallic form. |
| Hg | rhombohedral | 6 nearest neighbours | this structure can be considered to be a distorted hcp lattice with the nearest neghbours in the same plane being approx 16% further away [1] |
| Bi | rhombohedral | puckered sheet; each Bi atom has 3 neighbours in the same sheet at 307.2 pm; 3 in adjacent sheet at 352.9 pm.[1] | |
| Po | cubic | ||
| La | hexagonal | 12 nearest neighbours | "double hcp" with a layer structure ABAC...[2] |
| Pr | hexagonal | 12 nearest neighbours | "double hcp" with a layer structure ABAC...[2] |
| Nd | hexagonal | 12 nearest neighbours | "double hcp" with a layer structure ABAC...[2] |
| Sm | hexagonal | 12 nearest neighbours | complex hcp with 9 layer repeat, ABCBCACAB....[2] |
| Pa | tetragonal | body centred tetragonal unit cell, which can be considered to be a distorted bcc | |
| U | orthorhombic | ||
| Np | orthorhombic [3] | ||
| Pu | monoclinic |
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 each layer is positioned relative to others. Whilst there are many ways can be envisaged for a regular build up of layers:
In the ideal hcp structure the unit cell axial ratio is 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. In others e.g. zinc the deviations from the ideal change the symmetry of the structure.
More content relating to number of planes within structure and implications for glide/slide e.g. ductility.
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 included. Note that if the body centered cubic unit cell is compressed along one 4 fold axis the structure becomes face centred cubic (cubic close packed).
Melting points are chosen as a simple, albeit crude, measure of the stability or strength of the metallic lattice. Some simple trends can be noted. Firstly the transition metals have generally higher melting points than the others. In alkali metals (group 1) and alkaline earth metals (group 2) the melting point decreases as atomic number increases, but in the transition metals the melting points if anything increase. Across a period the melting points reach a maximum at around group 6 and then fall with increasing atomic number.
in general the s-block elements have a lower melting point than d-block elements. the s block elements have metallic bond between their various atoms. the atoms of the d-block elements have covalent bond along with the metallic bond present. so the strength of interactions is more in the elements of d-block.
|
|||||||||||||||||||||||