The identity of any chemical element is determined solely by the number of protons residing in its atomic nucleus. This count is known as the atomic number, which serves as the organizing principle for the periodic table. To understand Bismuth (Bi), the first step is to establish this defining number, as it dictates all of the element’s chemical properties.
The Defining Number
Bismuth (Bi) possesses exactly 83 protons within its nucleus. This number is designated by the atomic number (\(Z = 83\)), which is positioned directly above the element’s symbol on the periodic table. The presence of 83 protons defines Bismuth, as no other element shares this characteristic. This fixed number determines the structure and chemical behavior of the Bismuth atom.
If an atom contained 82 protons, it would be Lead, and 84 protons would be Polonium. Changing the number of protons requires a nuclear reaction, resulting in the transmutation of the element into a new substance. Therefore, the answer to how many protons Bismuth has is 83, as this is the element’s immutable atomic signature.
Beyond Protons: Neutrons and Electrons
While the proton count fixes the element’s identity, an atom also contains neutrons and electrons. Neutrons reside alongside protons in the nucleus, contributing to the atom’s mass but carrying no electrical charge. The number of neutrons can vary, creating different forms of the element called isotopes, but this variation does not change the element’s name. The only naturally occurring isotope, Bismuth-209, contains 126 neutrons (209 minus 83 protons).
In a neutral Bismuth atom, the number of electrons orbiting the nucleus is exactly 83, balancing the positive charge of the protons. This balance ensures the atom is electrically neutral until it participates in a chemical bond. Bismuth atoms typically shed three outer electrons during reactions, resulting in a positively charged ion.
Key Characteristics of Bismuth
Bismuth is a dense, brittle metal with a silvery-white color that often shows an iridescent rainbow tarnish due to surface oxidation. It is one of the few substances that expands as it freezes, a physical property it shares with water. This characteristic is utilized in low-melting alloys, such as those found in fire detection and electrical fuses.
Compounds of Bismuth are widely used in pharmaceuticals, most notably in the common upset stomach remedy, Pepto-Bismol, which utilizes bismuth subsalicylate. Bismuth oxychloride is also used in cosmetics to give products a pearlescent sheen. While Bismuth-209 was long thought to be the heaviest stable element, it was discovered in 2003 to be radioactive. However, its half-life of over \(2.01 \times 10^{19}\) years is billions of times longer than the estimated age of the universe, rendering it practically stable.