NASA’s Cassini-Huygens mission detected a large cloud of toxic hydrogen cyanide (HCN) on Titan, one of Saturn’s moons. Titan also contains ethane (H
3 CCH
3 ), acetylene (HCCH), and ammonia (NH
3 ). What are the Lewis structures of these molecules?
Draw a skeleton and connect the atoms with single bonds. Remember that H is never a central atom:
Where needed, distribute electrons to the terminal atoms: HCN: six electrons placed on N
H
3 CCH
3 : no electrons remain
HCCH: no terminal atoms capable of accepting electrons
NH
3 : no terminal atoms capable of accepting electrons
Where needed, place remaining electrons on the central atom: HCN: no electrons remain
H
3 CCH
3 : no electrons remain
HCCH: four electrons placed on carbon
NH
3 : two electrons placed on nitrogen
Where needed, rearrange electrons to form multiple bonds in order to obtain an octet on each atom: HCN: form two more C–N bonds
H
3 CCH
3 : all atoms have the correct number of electrons
HCCH: form a triple bond between the two carbon atoms
NH
3 : all atoms have the correct number of electrons
Check your learning
Both carbon monoxide, CO, and carbon dioxide, CO
2 , are products of the combustion of fossil fuels. Both of these gases also cause problems: CO is toxic and CO
2 has been implicated in global climate change. What are the Lewis structures of these two molecules?
Carbon soot has been known to man since prehistoric times, but it was not until fairly recently that the molecular structure of the main component of soot was discovered. In 1996, the Nobel Prize in Chemistry was awarded to Richard
Smalley (
[link] ), Robert Curl, and Harold Kroto for their work in discovering a new form of carbon, the C
60 buckminsterfullerene molecule (
[link] ). An entire class of compounds, including spheres and tubes of various shapes, were discovered based on C
60. This type of molecule, called a fullerene, shows promise in a variety of applications. Because of their size and shape, fullerenes can encapsulate other molecules, so they have shown potential in various applications from hydrogen storage to targeted drug delivery systems. They also possess unique electronic and optical properties that have been put to good use in solar powered devices and chemical sensors.
Richard Smalley (1943–2005), a professor of physics, chemistry, and astronomy at Rice University, was one of the leading advocates for fullerene chemistry. Upon his death in 2005, the US Senate honored him as the “Father of Nanotechnology.” (credit: United States Department of Energy)
Exceptions to the octet rule
Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories:
Odd-electron molecules have an odd number of valence electrons, and therefore have an unpaired electron.
Electron-deficient molecules have a central atom that has fewer electrons than needed for a noble gas configuration.
Hypervalent molecules have a central atom that has more electrons than needed for a noble gas configuration.
Questions & Answers
Discuss the differences between taste and flavor, including how other sensory inputs contribute to our perception of flavor.
The lymphatic system plays several crucial roles in the human body, functioning as a key component of the immune system and contributing to the maintenance of fluid balance. Its main functions include:
1. Immune Response: The lymphatic system produces and transports lymphocytes, which are a type of
asegid
to transport fluids fats proteins and lymphocytes to the blood stream as lymph
Anatomy is the study of the structure of the body, while physiology is the study of the function of the body. Anatomy looks at the body's organs and systems, while physiology looks at how those organs and systems work together to keep the body functioning.
Enzymes are proteins that help speed up chemical reactions in our bodies. Enzymes are essential for digestion, liver function and much more. Too much or too little of a certain enzyme can cause health problems
Kamara
yes
Prince
how does the stomach protect itself from the damaging effects of HCl
the normal temperature is 37°c or 98.6 °Fahrenheit is important for maintaining the homeostasis in the body
the body regular this temperature through the process called thermoregulation which involves brain skin muscle and other organ working together to maintain stable internal temperature
