Template:HideTOC 24.1: Insulated Nanowires 24.2: The Main-Group Elements- Bonding and Properties The chemistry of the third-period element in a group is most representative of the chemistry of the group because the chemistry of the second-period elements is dominated by their small radii, energetically unavailable d orbitals, and tendency to form π bonds with other atoms. 24.3: The Most Common Matter- Silicates Silicon, the second most abundant element on earth, is an essential part of the mineral world. Its stable tetrahedral configuration makes it incredibly versatile and is used in various way in our every day lives. Found in everything from spaceships to synthetic body parts, silicon can be found all around us, and sometimes even in us. Silicates are some of the most abundant minerals on Earth. They are some of the most common raw material that takes over 75% of the Earth's crust. 24.4: Boron and Its Amazing Structures Elemental boron is a semimetal that is remarkably unreactive. Boron forms unique and intricate structures that contain multicenter bonds, in which a pair of electrons holds together three or more atoms. Elemental boron can be induced to react with many nonmetallic elements to give binary compounds that have a variety of applications. 24.5: Carbon, Carbides, and Carbonates The stability of the carbon tetrahalides decreases as the halogen increases in size because of poor orbital overlap and steric crowding. Carbon forms three kinds of carbides with less electronegative elements: ionic carbides, which contain metal cations and C4− (methide) or C22− (acetylide) anions; interstitial carbides, which are characterized by covalent metal–carbon interactions and are among the hardest substances known; and covalent carbides, which have three-dimensional covalent network st 24.6: Nitrogen and Phosphorus- Essential Elements for Life Nitrogen behaves chemically like nonmetals, Nitrogen forms compounds in nine different oxidation states. Nitrogen does not form stable catenated compounds because of repulsions between lone pairs of electrons on adjacent atoms, but it does form multiple bonds with other second-period atoms. Nitrogen reacts with electropositive elements to produce solids that range from covalent to ionic in character. 24.7: Oxygen Oxygen is an element that is widely known by the general public because of the large role it plays in sustaining life. Without oxygen, animals would be unable to breathe and would consequently die. Oxygen is not only important to supporting life, but plays an important role in many other chemical reactions. Oxygen is the most common element in the earth's crust and makes up about 20% of the air we breathe. Historically the discovery of oxygen as an element essential for combustion. 24.8: Sulfur- A Dangerous and Useful Element Sulfur (group 16) reacts with almost all metals and readily forms the sulfide ion, S2−, in which it has as oxidation state of 2−. Sulfur reacts with most nonmetals. 24.9: Halogens- Reactive Chemicals with High Electronegativity The halogens are highly reactive. All halogens have relatively high ionization energies, and the acid strength and oxidizing power of their oxoacids decreases down the group. The halogens are so reactive that none is found in nature as the free element; instead, all but iodine are found as halide salts with the X− ion. Their chemistry is exclusively that of nonmetals. Consistent with periodic trends, ionization energies decrease down the group. 24.E: Chemistry of the Nonmetals (Exercises)