Sulfur hexafluoride

Sulfur hexafluoride (SF₆) is an inorganic, colorless, odorless, non-flammable, extremely potent greenhouse gas which is an excellent electrical insulator.SF
6 has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom. It is a hypervalent molecule. Typical for a nonpolar gas, it is poorly soluble in water but soluble in nonpolar organic solvents. It is generally transported as a liquefied compressed gas. It has a density of 6.12 g/L at sea level conditions, which is considerably higher than the density of air (1.225 g/L).

Synthesis and reactions

SF
6 can be prepared from the elements through exposure of S
8 to F
2. This was also the method used by the discoverers Henri Moissan and Paul Lebeau in 1901. Some other sulfur fluorides are cogenerated, but these are removed by heating the mixture to disproportionate any S
2F
10 (which is highly toxic) and then scrubbing the product with NaOH to destroy remaining SF
4.

There is virtually no reaction chemistry for SF
6. A main contribution to the inertness of SF₆ is the steric hindrance of the sulfur atom, whereas its heavier group 16 counterparts, such as SeF₆ are more reactive than SF₆ as a result of less steric hindrance (See hydrolysis example). It does not react with molten sodium below its boiling point, but reacts exothermically with lithium.

Circuit breaker

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by Overcurrent/overload or short circuit. Its basic function is to interrupt current flow after Protective relays detect faults condition. Unlike a fuse, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city.

Origins

Steve Spangler

Steve Spangler (born December 8, 1966) is a television personality, author and science teacher. Spangler founded Steve Spangler Science and its wholesale division, Be Amazing Toys. He serves as CEO of Steve Spangler Science and the creative director of Be Amazing Toys. Both companies develop science education teaching tools and toys. Spangler posted the first Diet Coke and Mentos video on YouTube in September 2005 and his 2002 televised demonstration of the eruption went viral launching a chain of several other Diet Coke and Mentos experiment viral videos. He earned two Heartland Emmy Awards and a total of five Emmy nominations. Spangler holds a Guinness World Record for the largest physics lesson and is an inductee of the National Speakers Association Speaker Hall of Fame.

Career

Education work

Spangler's career began as a science teacher in the Cherry Creek School District in Colorado. As part of a science outreach program, Spangler created a traveling science show targeted to elementary and middle school students in an effort to increase interest in science. In 1991, Spangler began traveling throughout Colorado and the surrounding states to present school assembly programs and teacher training workshops focused on using more inquiry-based science activities in the classroom.

Circuit

Circuit may refer to:

In government and law

In media

In science and technology

In electrical engineering

Lewis structure

Lewis structures (also known as Lewis dot diagrams, electron dot diagrams, Lewis dot formulas, Lewis dot structures, and electron dot structures) are diagrams that show the bonding between atoms of a molecule and the lone pairs of electrons that may exist in the molecule. A Lewis structure can be drawn for any covalently bonded molecule, as well as coordination compounds. The Lewis structure was named after Gilbert N. Lewis, who introduced it in his 1916 article The Atom and the Molecule. They are similar to electron dot diagrams in that the valence electrons in lone pairs are represented as dots, but they also contain lines to represent shared pairs in a chemical bond (single, double, triple, etc.).

Lewis structures show each atom and its position in the structure of the molecule using its chemical symbol. Lines are drawn between atoms that are bonded to one another (pairs of dots can be used instead of lines). Excess electrons that form lone pairs are represented as pairs of dots, and are placed next to the atoms.