The identity and charge of any chemical species are determined by the count of its subatomic particles. Protons, which reside in the nucleus, establish the element’s identity, while the number of electrons dictates the overall electrical charge. The imbalance between these charged particles defines whether the species is a neutral atom or a charged ion.
Determining Element Identity from Proton Count
The defining characteristic of any element is its atomic number, which is equivalent to the number of protons in the nucleus. The element with exactly 34 protons is Selenium (Se). Selenium is positioned in Group 16 and Period 4 of the periodic table, classifying it as a nonmetal. Its placement in Group 16 indicates that it shares similar chemical properties with oxygen and sulfur.
Calculating the Resulting Ionic Charge
The difference between the number of protons and the number of electrons determines the net electrical charge of the species. When these numbers differ, the atom is called an ion. With 34 positively charged protons and 36 negatively charged electrons, the net charge is negative two (34 – 36 = -2). Therefore, the species formed is an anion, specifically the Selenide ion (Se2-). This negative two charge is the most common and stable ionic form for elements in Group 16, as gaining two electrons achieves the stable electron configuration of the nearest noble gas, Krypton.
The Essential Role of Selenium
Biological Role
Selenium is recognized as a required trace mineral for human and animal health. It performs biological functions primarily through its incorporation into selenoproteins. The human genome contains genes for 25 different selenoproteins involved in numerous physiological processes.
One of the most studied selenoproteins is glutathione peroxidase (GPx), a powerful antioxidant enzyme. This enzyme protects cells from oxidative damage caused by reactive oxygen species. Selenium is also involved in the metabolism of thyroid hormones, acting as a cofactor for the deiodinase enzymes.
Maintaining appropriate Selenium intake is important, as the range between deficiency and toxicity is narrow. Deficiency is linked to Keshan disease, a form of cardiomyopathy. Excessive intake can lead to Selenosis, characterized by symptoms such as hair loss, brittle nails, and gastrointestinal issues.
Industrial Applications
The element also has significant applications outside of biological systems, leveraging its electrical and optical properties. Selenium is a semiconductor, and its photoconductive nature made it historically important in photocells and xerography. Modern industrial uses include glass manufacturing, where it can decolorize glass or create a red hue. It is also a component in CIGS thin-film solar cells, and selenium sulfide is used in anti-dandruff shampoos due to its antifungal properties.