Chemical element isotopes: specifically the elements without any stable isotopes are technetium (atomic number 43), promethium (atomic number 61), and all observed elements with atomic numbers greater than 82. Of the 80 elements with at least one stable isotope, 26 have only one single stable isotope. The mean number of stable isotopes for the 80 stable elements is 3.1 stable isotopes per element. The largest number of stable isotopes that occur for a single element is 10 (for tin, element 50). The mass number of an element, "A", is the number of nucleons (protons and neutrons) in the atomic nucleus. Different isotopes
Fire (classical element) temperament (of a person dominated by the yellow bile humour); the masculine; and the eastern point of the compass. In alchemy the chemical element of sulfur was often associated with fire and its alchemical symbol and its symbol was an upward-pointing triangle. In alchemic tradition, metals are incubated by fire in the womb of the Earth and alchemists only accelerate their development. Agni is a Hindu and Vedic deity. The word "agni" is Sanskrit for fire (noun), cognate with Latin "ignis" (the root of English "ignite"), Russian "огонь" (fire), pronounced "agon". Agni has three forms: fire, lightning and the sun.