Dividing line between metals and nonmetals

1 2 12 13 14 15 16 17 18
  H
                 He
  
Li
 Be
 B
 C
 N
 O
 F
 Ne
Na
 Mg
 Al
 Si
 P
 S
 Cl
 Ar
K
 Ca
 Zn
 Ga
 Ge
 As
 Se
 Br
 Kr
Rb
 Sr
 Cd
 In
 Sn
 Sb
 Te
 I
 Xe
Cs
 Ba
 Hg
 Tl
 Pb
 Bi
 Po
 At
 Rn
Fr
 Ra
 Cn
 Nh
 Fl
 Mc
 Lv
 Ts
 Og
Condensed periodic table showing a typical metal–nonmetal dividing line.
  Elements commonly recognised as metalloids (boron, silicon, germanium, arsenic, antimony and tellurium) and those inconsistently recognised as such (polonium and astatine)
  Metal-nonmetal dividing line (arbitrary): between Li and H, Be and B, Al and Si, Ge and As, Sb and Te, Po and At, Ts and Og

The dividing line between metals and nonmetals can be found, in varying configurations, on some representations of the periodic table of the elements (see mini-example, right). Elements to the lower left of the line generally display increasing metallic behaviour; elements to the upper right display increasing nonmetallic behaviour. When presented as a regular stair-step, elements with the highest critical temperature for their groups (Li, Be, Al, Ge, Sb, Po) lie just below the line.[1]

Names

This line has been called the amphoteric line,[2] the metal-nonmetal line,[3] the metalloid line,[4][5] the semimetal line,[6] or the staircase.[2][n 1] It is also erroneously referred to as the Zintl border[8] or the Zintl line.[9][10] The last two terms instead refer to a vertical line sometimes drawn between groups 13 and 14. This particular line was christened by Laves in 1941.[11] It differentiates group 13 elements from those in and to the right of group 14. The former generally combine with electropositive metals to make intermetallic compounds whereas the latter usually form salt-like compounds.[12]

History

References to a dividing line between metals and nonmetals appear in the literature as far back as at least 1869.[13] In 1891, Walker published a periodic 'tabulation' with a diagonal straight line drawn between the metals and the nonmetals.[14] In 1906, Alexander Smith published a periodic table with a zigzag line separating the nonmetals from the rest of elements, in his highly influential[15] textbook Introduction to General Inorganic Chemistry.[16] In 1923, Horace G. Deming, an American chemist, published short (Mendeleev style) and medium (18-column) form periodic tables.[17] Each one had a regular stepped line separating metals from nonmetals. Merck and Company prepared a handout form of Deming's 18-column table, in 1928, which was widely circulated in American schools. By the 1930s Deming's table was appearing in handbooks and encyclopaedias of chemistry. It was also distributed for many years by the Sargent-Welch Scientific Company.[18][19][20]

Double line variant

A dividing line between metals and nonmetals is sometimes replaced by two dividing lines. One line separates metals and metalloids; the other metalloids and nonmetals.[21][22]

Concerns

Mendeleev wrote that, 'It is ... impossible to draw a strict line of demarcation between metals and nonmetals, there being many intermediate substances'.[23][n 2][n 3] Several other sources note confusion or ambiguity as to the location of the dividing line;[26][27] suggest its apparent arbitrariness[28] provides grounds for refuting its validity;[29] and comment as to its misleading, contentious or approximate nature.[30][31][32] Deming himself noted that the line could not be drawn very accurately.[33]

Notes

  1. ↑ Sacks[7] described the dividing line as, 'A jagged line, like Hadrian's Wall ... [separating] the metals from the rest, with a few "semimetals," metalloids—arsenic, selenium—straddling the wall.'
  2. ↑ In the context of Mendeleev's observation, Glinka[24] adds that: 'In classing an element as a metal or a nonmetal we only indicate which of its properties—metallic or nonmetallic—are more pronounced in it'.
  3. ↑ Mendeleev regarded tellurium as such an intermediate substance: '... it is a bad conductor of heat and electricity, and in this respect, as in many others, it forms a transition from the metals to the nonmetals.'[25]

Citations

  1. ↑ Horvath 1973, p. 336
  2. 1 2 Levy 2001, p. 158
  3. ↑ Tarendash 2001, p. 78
  4. ↑ Thompson 1999
  5. ↑ DiSalvo 2000, p. 1800
  6. ↑ Whitley 2009
  7. ↑ Sacks 2001, pp. 191, 194
  8. ↑ King 2005, p. 6006
  9. ↑ Herchenroeder & Gschneidner 1988
  10. ↑ De Graef & McHenry 2007, p. 34
  11. ↑ Kniep 1996, p. xix
  12. ↑ Nordell & Miller 1999, p. 579
  13. ↑ Hinrichs 1869, p. 115. In his article Hinrichs included a periodic table, organized by atomic weight, but this did not show a metal-nonmetal dividing line. Rather, he wrote that, '... elements of like properties or their compounds of like properties, form groups bounded by simple lines. Thus a line drawn through C, As, Te, separates the elements, having metallic lustre from those not having such lustre. The gaseous elements form a small group by themselves, the condensible [sic] chlorine forming the boundary ... So also the boundary lines for other properties may be drawn.'
  14. ↑ Walker 1891, p. 252
  15. ↑ Miles & Gould 1976, p. 444: 'His "Introduction to General Inorganic Chemistry," 1906, was one of the most important textbooks in the field during the first quarter of the twentieth century.'
  16. ↑ Smith 1906, pp. 408, 410
  17. ↑ Deming 1923, pp. 160, 165
  18. ↑ Abraham, Coshow & Fix, W 1994, p. 3
  19. ↑ Emsley 1985, p. 36
  20. ↑ Fluck 1988, p. 432
  21. ↑ Brown & Holme 2006, p. 57
  22. ↑ Swenson 2005
  23. ↑ Mendeléeff 1897, p. 23
  24. ↑ Glinka 1959, p. 77
  25. ↑ Mendeléeff 1897, p. 274
  26. ↑ MacKay & MacKay 1989, p. 24
  27. ↑ Norman 1997, p. 31
  28. ↑ Whitten, Davis & Peck 2003, p. 1140
  29. ↑ Roher 2001, pp. 4–6
  30. ↑ Hawkes 2001, p. 1686
  31. ↑ Kotz, Treichel & Weaver 2005, pp. 79–80
  32. ↑ Housecroft & Constable 2006, p. 322
  33. ↑ Deming 1923, p. 381

References

External links

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