Editing Mendeleev's predicted elements (section)

== Original predictions ==
{{Periodic table (micro)|title=Mendeleev's predicted elements|caption=(as located in the modern periodic table)|mark=Sc,Ga,Tc,Ge}} 
The four predicted elements lighter than the [[rare-earth element]]s, ''eka-[[boron]]'' (''Eb'', under boron, B, 5), ''eka-[[aluminium]]'' (''Ea'' or ''El'',<ref name="Mendeleev1871">{{Cite journal |last=Mendeleev |first=D. I. |date=1871 |title=The natural system of elements and its application to the indication of the properties of undiscovered elements (in Russian) |url=http://heritage.jscc.ru/Book/10073622 |journal=Journal of the Russian Chemical Society |volume=3 |issue=7 |pages=25–56}}</ref> under Al, 13), ''eka-[[manganese]]'' (''Em'', under Mn, 25), and ''eka-[[silicon]]'' (''Es'', under Si, 14), proved to be good predictors of the properties of [[scandium]] (Sc, 21), [[gallium]] (Ga, 31), [[technetium]] (Tc, 43), and [[germanium]] (Ge, 32) respectively, each of which fill the spot in the periodic table assigned by Mendeleev.

The names were written by Dmitri Mendeleev as {{wikt-lang|ru|экаборъ}} ([[wikt:Wiktionary:Russian transliteration|ekabor]]), {{wikt-lang|ru|экаалюминій}} ([[wikt:Wiktionary:Russian transliteration|ekaaljuminij]]), {{wikt-lang|ru|экамарганецъ}} ([[wikt:Wiktionary:Russian transliteration|ekamarganec]]), and {{wikt-lang|ru|экасилицій}} ([[wikt:Wiktionary:Russian transliteration|ekasilicij]]) respectively, following the [[Reforms of Russian orthography#The post-revolution reform|pre-1917 Russian orthography]].

Initial versions of the periodic table did not distinguish [[rare earth element]]s from [[transition element]]s, helping to explain both why Mendeleev's predictions for heavier unknown elements did not fare as well as those for the lighter ones and why they are not as well known or documented.

[[Scandium oxide]] was isolated in late 1879 by [[Lars Fredrick Nilson]]; [[Per Teodor Cleve]] recognized the correspondence and notified Mendeleev late in that year. Mendeleev had predicted an [[atomic mass]] of 44 for [[ekaboron|eka-boron]] in 1871, while scandium has an atomic mass of 44.955907.

In 1871, Mendeleev predicted<ref name="Mendeleev1871" /> the existence of a yet-undiscovered element he named eka-aluminium (because of its proximity to [[aluminium]] in the [[periodic table]]). The table below compares the qualities of the element predicted by Mendeleev with actual characteristics of gallium, which was discovered, soon after Mendeleev predicted its existence, in 1875 by [[Paul Emile Lecoq de Boisbaudran]].

{| class="wikitable"
! colspan=2|Property
! Eka-aluminium
! Gallium
|-
| colspan=2|Atomic Mass
| 68
| 69.723
|-
| colspan=2|Density (g/cm<sup>3</sup>)
| 6.0
| 5.91
|-
| colspan=2|Melting point (°C)
| Low
| 29.76
|-
| rowspan=3|Oxide
|Formula
| Ea<sub>2</sub>O<sub>3</sub>
| Ga<sub>2</sub>O<sub>3</sub>
|-
| Density
|5.5&nbsp;g/cm<sup>3</sup>
|5.88&nbsp;g/cm<sup>3</sup>
|-
|Solubility
| colspan=2|Soluble in both alkalis and acids
|-
|rowspan=2|Chloride
|Formula
| Ea<sub>2</sub>Cl<sub>6</sub>
| Ga<sub>2</sub>Cl<sub>6</sub>
|-
|Volatility
| Volatile
| Volatile
|}

[[Technetium]] was isolated by [[Carlo Perrier]] and [[Emilio Segrè]] in 1937, well after Mendeleev's lifetime, from samples of [[molybdenum]] that had been bombarded with [[deuterium]] nuclei in a [[cyclotron]] by [[Ernest Lawrence]].  Mendeleev had predicted an atomic mass of 100 for eka-manganese in 1871, and the most stable isotopes of technetium are <sup>97</sup>Tc and <sup>98</sup>Tc.<ref>These are [[mass number|mass numbers]] of 97 and 98 which are different from an atomic mass in that they are counts of nucleons in the nuclei of some [[isotope|isotopes]] and are not the [[Standard atomic weight|atomic weight]] of an average sample (with a natural collection of isotopes). The <sup>97</sup>Tc and <sup>98</sup>Tc isotopes have respectively an atomic mass of 96.9063607 and 97.9072112, and respectively a half-life of {{val|4.21|e=6}} years and {{val|4.2|e=6}} years. For elements that are not stable enough to persist from the creation of the Earth, the convention is to report the atomic mass number of the most stable isotope in place of the naturally occurring atomic-mass average. {{cite web |url=http://chemlab.pc.maricopa.edu/PERIODIC/Tc.html |title=Technetium |access-date=2006-11-11 |url-status=dead |archive-url=https://web.archive.org/web/20061203025311/http://chemlab.pc.maricopa.edu/PERIODIC/Tc.html |archive-date=2006-12-03 }}.</ref>

Germanium was isolated in 1886 and provided the best confirmation of the theory up to that time, due to its contrasting more clearly with its neighboring elements than the two previously confirmed predictions of Mendeleev do with theirs.

{| class="wikitable"
! colspan=2|Property
! Eka-silicon
! Germanium
|-
| colspan=2|Atomic Mass
| 72
| 72.630
|-
| colspan=2|Density (g/cm<sup>3</sup>)
| 5.5
| 5.323
|-
| colspan=2|Melting point (°C)
| High
| 938
|-
| colspan=2|Color
| Grey
| Grey
|-
|rowspan=3|Oxide
| Type
| colspan=2|[[Refractory]] dioxide
|-
| Density (g/cm<sup>3</sup>)
| 4.7
| 4.228
|-
| Activity
| Feebly basic
| Feebly basic
|-
| rowspan=2|Chloride
|Boiling point
| Under 100&nbsp;°C
| 86.5&nbsp;°C (GeCl<sub>4</sub>)
|-
| Density (g/cm<sup>3</sup>)
| 1.9
| 1.879
|}