Atomic Mass and Mass Number Chemistry Review

Atomic Mass and Mass Number Chemistry Review Atomic mass and atomic mass number are two important concepts in chemistry. Heres a quick review of what is meant by atomic mass and atomic mass number, as well as how actual particle mass relates to atomic number. Atomic Definitions Z is used to signify the atomic number or proton number of an atomZ # of protons of an atomA is used to signify the atomic mass number (also known as atomic mass or atomic weight) of an atomA # protons # neutronsA and Z are integer valuesWhen the actual mass of an atom is expressed in amu (atomic mass units) or g/mol then the value is close to A Are Atomic Mass and Atomic Mass Number the Same? Yes and no. If you are talking about a sample of a single isotope of an element, the atomic mass number and the atomic mass are either very close or else the same. In introductory chemistry, its probably fine to consider them to mean the same thing. However, there are two cases in which the sum of the protons and neutrons (atomic mass number) is not quite the same as the atomic mass! In the periodic table, the atomic mass listed for an element reflects the natural abundance of the element. The atomic mass number of the isotope of hydrogen called protium is 1, while the atomic mass number of the isotope called deuterium is 2, yet the atomic mass is listed as 1.008. This is because natural elements are a mixture of isotopes. The other difference between the sum of protons and neutrons and the atomic mass is due to mass defect. In a mass defect, some of the mass of the protons and neutrons is lost when they bind together to form an atomic nucleus. In a mass defect, the atomic mass is lower than the atomic mass number. Source Jensen, William B. (2005). The Origins of the Symbols A and Z for Atomic Weight and Number. J. Chem. Educ. 82: 1764.

USS Langley - The US Navys First Aircraft Carrier

USS Langley - The US Navys First Aircraft Carrier Laid down on October 18, 1911, at the Mare Island Naval Shipyard in Vallejo, CA, USS Langley (CV-1) began its life as the Proteus-class collier USS Jupiter (AC-3). Its keel-laying ceremony was attended by President William H. Taft. Work continued through the winter and the collier was launched on April 14, 1912. The US Navys first turbo-electric-powered ship, Jupiter joined the fleet in April 1913, under the command of Commander Joseph M. Reeves. USS Jupiter Shortly after passing sea trials, Jupiter was sent south to the Mexican coast off Mazatln. Carrying a detachment of US Marines, the Navy hoped that the ships presence would aid in calming tensions during the 1914 Veracruz crisis. With the situation diffused, the collier departed for Philadelphia in October, becoming the first ship to transit the Panama Canal from west to east in the process. After service with the Atlantic Fleet Auxiliary Division in the Gulf of Mexico, Jupiter was switched to cargo duty in April 1917. Assigned to the Naval Overseas Transport Service, Jupiter sailed in support of US efforts during World War I, and made two cargo voyages to Europe (June 1917 and November 1918).   During its first Atlantic crossing, the collier carried a naval aviation detachment commanded by Lieutenant Kenneth Whiting. These were the first American military aviators to reach Europe. Returning to coaling duties in January 1919, Jupiter operated in European waters to facilitate the return of troops serving with the American Expeditionary Forces following the end of the war. Later that year, the ship received orders to return to Norfolk for conversion into an aircraft carrier. Arriving on December 12, 1919, the ship was decommissioned the following March. The US Navys First Aircraft Carrier Work began immediately to convert the ship, which was renamed in honor of aviation pioneer Samuel Pierpont Langley on April 21, 1920. In the yard, workers reduced the ships superstructure and built a flight deck over the length of the ship. The vessels two funnels were moved outboard and an elevator constructed for moving aircraft between decks. Completed in early 1922, Langley was designated CV-1 and commissioned on March 20, with Whiting, now a commander, in command. Entering service, Langley became the primary test platform for the US Navys budding aviation program.    USS Langley (CV-1) - Overview Type: Aircraft CarrierNation: United StatesBuilder: Mare Island Naval ShipyardLaid Down: October 18, 1911Launched: August 14, 1912Commissioned: March 20, 1922 Specifications Displacement: 11,500 tonsLength: 542 ft.Beam: 65 ft.Draft: 18 ft. 11 in.Speed: 15 knotsComplement: 468 officers and men Armament 55 aircraft4 Ãâ€" 5 guns Early Operations On October 17, 1922, Lieutenant Virgil C. Griffin became the first pilot to fly from the ships deck when he took off in his Vought VE-7-SF. The ships first landing came nine days later when Lieutenant Commander Godfrey de Courcelles Chevalier came aboard in an Aeromarine 39B. The firsts continued on November 18, when Whiting became the first naval aviator to be catapulted from a carrier when he launched in a PT. Steaming south in early 1923, Langley continued aviation testing in the warm waters of the Caribbean before sailing to Washington DC that June to conduct a flight demonstration and show its capabilities to governmental officials. Returning to active duty, Langley operated out of Norfolk for much of 1924, and underwent its first overhaul late that summer. Putting to sea that fall, Langley transited the Panama Canal and joined the Pacific Battle Fleet on November 29. For the next dozen years, the ship served with the fleet off Hawaii and California working to training aviators, conducting aviation experiments, and taking part in war games. With the arrival of the larger carriers Lexington (CV-2) and Saratoga (CV-3) and the near completion of Yorktown (CV-5) and Enterprise (CV-6), the Navy decided that the little Langley was no longer needed as a carrier. Seaplane Tender On October 25, 1936, Langley arrived at Mare Island Naval Shipyard for conversion into a seaplane tender. After removing the forward section of the flight deck, workers built a new superstructure and bridge, while the aft end of the ship was altered to accommodate the ships new role. Re-designated AV-3, Langley sailed in April 1937. Following a brief assignment in the Atlantic during early 1939, the ship sailed for the Far East, reaching Manila on September 24. When World War II began, the ship was anchored nearby at Cavite. On December 8, 1941, Langley departed the Philippines for Balikpapan, Dutch East Indies before finally making for Darwin, Australia. World War II During the first half of January 1942, Langley aided the Royal Australian Air Force in conducting anti-submarine patrols out of Darwin. Receiving new orders, the ship sailed north later that month to deliver 32 P-40 Warhawks to Allied forces at Tjilatjap, Java and to join American‑British‑Dutch‑Australian forces gathering to block the Japanese advance into Indonesia. On February 27, shortly after meeting with its antisubmarine screen, the destroyers USS Whipple and USS Edsall, Langley was attacked by a flight of nine Japanese G4M Betty bombers. Successfully evading the first two Japanese bombing runs, the ship was hit five times on the third, causing the topsides to burst in to flames and the ship to develop a 10-degree list to port. Limping towards Tjilatjap Harbor, Langley lost power and was unable to negotiate the mouth of the harbor. At 1:32 PM, the ship was abandoned and the escorts moved into sink the hulk to prevent its capture by the Japanese. Sixteen of Langleys crew were killed in the attack.