Class Notes Feb 6 PDF

Atomic Number and Mass Number The atomic number is given by the number of protons in the nucleus. Atomic number is what determines the identity of the atom. The mass number (simplified at this point) is the sum of the number of protons and the number of neutrons....

Atomic Number and Mass Number The atomic number is given by the number of protons in the nucleus. Atomic number is what determines the identity of the atom. The mass number (simplified at this point) is the sum of the number of protons and the number of neutrons. Hydrogen Atom (H) Atomic number: 1 (1 proton) Neutron number: 0 (0 neutrons) Mass number: 1 + 0 = 1 Oxygen Atom (O) Atomic number: 8 (8 protons) Neutron number: 8 (16 - 8 neutrons) Mass number: 8 + 8 = 16 1 Mass number and atomic mass are not the same. Isotopes are defined as forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei. Isotopes differ in relative atomic mass but not in chemical properties. The atomic mass of each element is the weighted average of the masses of all of the naturally occurring isotopes of the element.  6 protons 6 protons 6 protons 6 neutrons 7 neutrons 8 neutrons 6 electrons 6 electrons 6 electrons This makes it carbon! Relative Abundance: 12C 13C 14C 98.9% 1.1% 1300 C), so additives are used to lower the melting point, making the glass easier to work with. examples: sodium carbonate, Na2CO3, calcium carbonate, CaCO3, and magnesium carbonate, MgCO3) These elements end up as part of the amorphous structure of glass, with the most common type of glass being soda-lime glass. 10 From Sand to Glass Other additives: Various elements can be added to color to glass Many of these elements give minerals and gemstones natural color Citrine (left) and amethyst (right) both have trace amounts of iron that give them their 11 color  The Chemistry of Coloured Glass 12 From Sand to Glass Inside Corning's Gorilla Glass Factory (youtube.com) To increase strength of glass, the structure of the glass is changed at the surface. Corning’s Gorilla Glass soaks glass in molten KNO3 bath to replace sodium ions with larger potassium ions, increasing compression at the surface. Whereas normal glass can withstand a force of 7000 psi, Gorilla Glass can withstand >1,450,380 psi! © McGraw Hill 13 Cradle-to-Cradle Recycling Over 90% of cell phones are sent to landfills or are collected at homes. Only 3% are recycled! A sustainable life cycle for portable electronics is called “Cradle-to-Cradle” The end of usefulness of one product dovetails with the beginning of the life cycle for another product. © McGraw Hill 14 Three Pillars of Sustainability When considering the most responsible end-use of a product, one should consider three pillars of sustainability: Environmental: pollution prevention, natural resource use. Social: better quality of life for all members of society. Economic: fair distribution and efficient allocation of resources. © McGraw Hill 15 The Importance of Recycling Sections 1-9, 1-10 An average cell phone contains: 300 mg of silver 30 mg of gold The process of recycling electronics to recover metals is referred to as urban mining. While much electronics recycling is done by hand, some companies are developing disassembly robots to make the process safer and more environmentally friendly. © McGraw Hill 16 The Recycling Rates of Smartphone 17Metals The Recycling Rates of Smartphone 18Metals What Are the Rare Earths? Rare earth elements are a group of seventeen chemical elements that occur together in the periodic table. Rare earth metals are used for applications such as: Rechargeable batteries. Magnets. Speakers. Memory chips. Fluorescent lighting. Catalytic converters. Advanced electronics. Advanced weaponry. Rare Earth Elements, Explained – Global X ETFs © McGraw Hill 19 What Are the Rare Earths? rare earth, “get ready” 1969 Rare Earth Element Production: Cause for Concern This chart shows a history of rare earth element production, in metric tons of rare earth oxide equivalent, between 1950 and 2022. It clearly shows the United States' entry into the market in the mid-1960s when color television exploded demand.  Rare Earth Element Production: Cause for Concern When China began selling rare earths at very low prices in the late 1980s and early 1990s, mines in the United States were forced to close because they could no longer make a profit. When China cut exports in 2010, rare earth prices skyrocketed. That motivated new production in the United States, Australia, Russia, Thailand, Malaysia, and other countries. China controls most of the world’s supply of the rare earth metals. Over 90% comes from China who holds 50% of the world’s reserves. 22