What is the atomic mass number of the magnesium atom?
Debbie Holly 2. 4. Define compound and native element. Elements are those substances that alchemists, try as they might, could not divide into other substances. The different elements have different weights. Listed in order of increasing weight, the elements occur as groups of metals and nonmetals. In 1869, Dimitry Ivanovich Mendeleyev, famously dreamed that (and on awaking saw that) the line up of 63 then known elements could be broken so as to form a table with a column of metals and one of nonmetals. Gaps in the pattern could then indicate, he suggested, what was still to be found. He was right. Today, we can talk of a list of naturally occurring elements in the Periodic Table of Elements that runs from 1 (hydrogen, the lightest) to 92 (uranium, the heaviest). Of this list, missing in nature on earth is 42 (technetium, identified in the spectra “late-type” stars) and 61 (promethium, made only by physicists who, with atom smashing devices, can do what alchemists never could). Atomic
