Nucleus Definition in Chemistry

Nucleus Definition in Chemistry In chemistry, a nucleus is the positively charged center of the atom consisting of  protons and neutrons. Its also known as the atomic nucleus. The word nucleus comes from the Latin word nucleus, which is a form of the word nux, which means nut or kernel. The term was coined in 1844 by Michael Faraday to describe the center of an atom. The sciences involved in the study of the nucleus, its composition, and characteristics are called nuclear physics and nuclear chemistry. Protons and neutrons are held together by the strong nuclear force. Electrons, although attracted to the nucleus, move so fast they fall around it or orbit it at a distance. The positive electrical charge of the nucleus comes from the protons, while the neutrons have no net electrical charge. Nearly all the mass of an atom is contained within the nucleus since protons and neutrons have much more mass than electrons. The number of protons in an atomic nucleus defines its identity as an atom of a specific element. The number of neutrons determines which isotope of an element the atom is. Size The nucleus of an atom is much smaller than the overall diameter of the atom because the electrons can be distant from the atoms center. A hydrogen atom is 145,000 times larger than its nucleus, while a uranium atom is around 23,000 times larger than its nucleus. The hydrogen nucleus is the smallest nucleus because it consists of a lone proton. It is 1.75 femtometers (1.75 x 10-15 m). The uranium atom, in contrast, contains many protons and neutrons. Its nucleus is about 15 femtometers. Arrangement of Protons and Neutrons The protons and neutrons are usually depicted as  compacted together and evenly spaced into spheres. However, this is an oversimplification of the actual structure. Each nucleon (proton or neutron) can occupy a certain energy level and a range of locations. While a nucleus can be spherical, it may also be pear-shaped, rugby ball-shaped, discus-shaped, or triaxial. The protons and neutrons of the nucleus are baryons composed of smaller subatomic particles, called quarks. The strong force has an extremely short range, so protons and neutrons must be very near to each other to be bound. The attractive strong force overcomes the natural repulsion of the like-charged protons. Hypernucleus In addition to protons and neutrons, there is a third type of baryon called a hyperon. A hyperon contains at least one strange quark, while protons and neutrons consist of up and down quarks. A nucleus that contains protons, neutrons, and hyperons​ is called a hypernucleus. This type of atomic nucleus has not been seen in nature but has been formed in physics experiments. Halo Nucleus Another type of atomic nucleus is a halo nucleus. This is a core nucleus that is surrounded by an orbiting halo of protons or neutrons. A halo nucleus has a much larger diameter than a typical nucleus. Its also much more unstable than a normal nucleus. An example of a halo nucleus has been observed in lithium-11, which has a core consisting of 6 neutrons and 3 protons, with a halo of 2 independent neutrons. The half-life of the nucleus is 8.6 milliseconds. Several nuclides have been seen to have a halo nucleus when they are in the excited state, but not when they are in the ground state. Sources:   M. May (1994). Recent results and directions in hypernuclear and kaon physics. In A. Pascolini. PAN XIII: Particles and Nuclei. World Scientific. ISBN 978-981-02-1799-0. OSTI 10107402W. Nà ¶rtershuser, Nuclear Charge Radii of  Be and the One-Neutron Halo Nucleus  Be,  Physical Review Letters, 102:6, 13 February 2009,

History and Facts About Alcatraz Prison

History and Facts About Alcatraz Prison Once considered the prison of American prisons, the island of Alcatraz in San Francisco Bay has been an asset to the U.S. Army, the federal prison system, jailhouse folklore, and the historical evolution of the West Coast. Despite its reputation as a cold and unforgiving penitentiary, Alcatraz is now one of the most prominent tourist magnets in San Francisco. In 1775, Spanish explorer Juan Manuel de Ayala chartered what is now San Francisco Bay. He called the 22-acre rocky island La Isla de los Alcatraces, meaning Island of the Pelicans. With no vegetation or habitation, Alcatraz was little more than a desolate islet occupied by the occasional swarm of birds. Under the English-speaking influence, the name Alcatraces became Alcatraz. Fort Alcatraz Alcatraz was reserved for military use under President Millard Fillmore in 1850. Meanwhile, the discovery of gold in the Sierra Nevada Mountains brought growth and prosperity to San Francisco. The lure of the Gold Rush demanded the protection of California as gold seekers flooded the San Francisco Bay. In response, the U.S. Army built a fortress on the rocky face of Alcatraz. They made plans to install more than 100 cannons, making Alcatraz the most heavily armed entity on the West Coast. The first functional lighthouse on the West Coast was built on Alcatraz Island as well. Once fully equipped with weaponry in 1859, the island was deemed Fort Alcatraz. Having never fired its own weapons in combat, Fort Alcatraz quickly evolved from an island of defense to an island of detention. In the early 1860s, civilians arrested for treason during the Civil War were housed on the island. With the influx of prisoners, additional living quarters were built to house 500 men. Alcatraz as a jail would continue for 100 years. Throughout history, the average population of the island hovered between 200 and 300 people, never at maximum capacity. The Rock After the devastating San Francisco earthquake of 1906, inmates from nearby prisons were transferred to the infallible Alcatraz. Over the next five years, prisoners built a new jail, designated Pacific Branch, U.S. Military Prison, Alcatraz Island. Popularly known as The Rock, Alcatraz served as an army disciplinary barracks until 1933. Prisoners were educated and received military and vocational training here. Alcatraz of the early 20th century was a minimum-security prison. Prisoners spent their days working and learning. Some were even employed as babysitters for the families of prison officers. They eventually built a baseball field and inmates fashioned their own baseball uniforms. Boxing matches among inmates known as â€Å"Alcatraz Fights† were hosted on Friday nights. Prison life played a role in the changing landscape of the island. The military transported soil to Alcatraz from nearby Angel Island, and many prisoners were trained as gardeners. They planted roses, bluegrass, poppies, and lilies. Under the order of the U.S. Army, Alcatraz was a fairly mild institution and its accommodations were favorable. The geographic location of Alcatraz was the undoing of U.S. Army occupation. Importing food and supplies to the island was much too expensive. The Great Depression of the 1930s forced the army off the island, and the prisoners were transferred to institutes in Kansas and New Jersey. Uncle Sam’s Devil’s Island Alcatraz was obtained by the Federal Bureau of Prisons in 1934. The former military detention center became America’s first maximum-security civilian penitentiary. This â€Å"prison system’s prison† was specifically designed to house the most horrendous prisoners, the troublemakers that other federal prisons could not successfully detain. Its isolated location made it ideal for the exile of hardened criminals, and a strict daily routine taught inmates to follow prison rule and regulation. The Great Depression witnessed some of the most heinous criminal activity in modern American history, and Alcatraz’s severity was well suited to its time. Alcatraz was home to notorious criminals including Al â€Å"Scarface† Capone, who was convicted of tax evasion and spent five years on the island. Alvin â€Å"Creepy† Karpis, the FBI’s first â€Å"Public Enemy,† was a 28-year resident of Alcatraz. The most famous prisoner was Alaskan murderer Robert â€Å"Birdman† Stroud, who spent 17 years on Alcatraz. Over its 29 years of operation, the federal prison housed more than 1,500 convicts. Daily life in the Alcatraz Federal Penitentiary was harsh. Prisoners were given four rights. They included medical attention, shelter, food, and clothing. Recreational activities and family visits had to be earned through hard work. Punishments for bad behavior included hard labor, wearing a 12-pound ball and chain, and lock-downs where prisoners were kept in solitary confinement, restricted to bread and water. There was a total of 14 escape attempts by over 30 prisoners. Most were caught, several were shot, and a few were swallowed by the chilling swells of the San Francisco Bay. Why Did Alcatraz Close? The prison on Alcatraz Island was expensive to operate, as all supplies had to be brought in by boat. The island had no source of fresh water, and almost one million gallons were shipped in each week. Building a high-security prison elsewhere was more affordable for the Federal Government, and as of 1963 â€Å"Uncle Sam’s Devil’s Island† was no more. Today, the equivalent of the infamous federal prison on Alcatraz Island is a maximum-security institution in Florence, Colorado. It is nicknamed â€Å"Alcatraz of the Rockies†. Tourism Alcatraz Island became a national park in 1972 and is considered part of the Golden Gate National Recreation Area. Open to the public in 1973, Alcatraz sees more than one million visitors from across the globe each year. Alcatraz is best known as a maximum-security prison. Media attention and fantastic stories have exaggerated this image. The San Francisco Bay islet has been much more than this. Alcatraz as a mass of rock named for its birds, an American fort during the Gold Rush, an army barracks, and tourist attraction may be less enticing but allude to a more dynamic existence. It is one to be embraced by San Francisco and California as a whole.