Antimony is a lustrous gray metalloid element, designated by the chemical symbol Sb. It has been recognized since ancient times, with its compounds used in Egyptian cosmetics and early medicines. Antimony, like all elements, cannot be reduced to simpler substances solely through chemical reactions.
What Defines a Chemical Element
The definition of a chemical element is a species of atom defined by its unique number of protons. For Antimony, this number is 51, its atomic number. This count of positively charged protons, housed within the dense atomic nucleus, determines the element’s identity and its position on the periodic table.
Chemical reactions, by contrast, are governed entirely by the interaction of electrons that orbit the nucleus. These processes involve the sharing, giving, or taking of electrons to form chemical bonds, which creates compounds. Since the number of protons—the defining characteristic of the element—is completely unaffected by the movement of electrons, chemical manipulation can never change an Antimony atom into an atom of a different element.
Antimony’s Reactive Nature
While chemical means cannot break down Antimony into simpler elements, they can change its form and combine it with other substances. Antimony is a relatively stable solid at room temperature, but it readily reacts when heated. For example, when heated in air, it oxidizes to form compounds like antimony trioxide (Sb2O3), or it can be combined with sulfur to create stibnite (Sb2S3), its primary natural ore.
The Antimony atom can also exist in several distinct physical forms, known as allotropes. The most common is a stable, silvery-gray metallic form, but there are also metastable forms, including black and yellow Antimony. The black allotrope is significantly more chemically reactive than the metallic version, but it is unstable and will convert back to the stable metallic state if heated to about 100°C. In all these reactions and transformations, the core Antimony atom remains intact and can be chemically recovered to its pure, elemental state.
Changing Elements Through Nuclear Processes
The only way to fundamentally change an element like Antimony is through a process that alters the number of protons in its nucleus, which is termed nuclear transmutation. This is distinct from chemistry because it requires overcoming the powerful forces that bind the nucleus together. Transmutation can occur naturally through radioactive decay, where an unstable isotope spontaneously emits particles to become a different element.
Antimony has two stable isotopes, 121Sb and 123Sb, but also many artificial, unstable isotopes. For instance, the radioactive isotope 119Sb undergoes decay, which changes the number of protons and transforms it into an atom of tin (119Sn). Transmutation can also be induced artificially in a laboratory by bombarding the nucleus with high-energy particles, forcing a change in the atomic structure.