The long-standing model of pigment cell origins is implicitly based upon a progressive fate restriction model of neural crest development and postulates the existence of a partially restricted progenitor common to all pigment cell types (i.e., a chromatoblast) [38] .
Sodium is the fourth most abundant element on earth, comprising about 2.6% of the earth's crust; it is the most abundant of the alkali group of metals. It is now obtained commercially by the electrolysis of absolutely dry fused sodium chloride.
Sodium is a highly reactive soft greyish metal in its pure form, which is never found in nature because of said reactivity. Anyhow, to task: sodium has eleven (11) electrons, in a 2-8â1 configuration, with that one lonely valence electron in the outermost orbital/shell, accounting for the high degree of reactivity. In the nucleus are eleven (11) protons and twelve (12) neutrons. The only stable isotope of sodium is 24Na, which can only be formed thru nucleosynthesis at temperatures approaching 600 megakelvins.