Covalent bond in methane

Caibon has eight electrons in its valence shell in both methane and carbon tetrafluoride. By forming covalent bonds to four other atoms, carbon achieves a stable electron configuration analogous to neon. Each covalent bond in methane and carbon tetrafluoride is quite strong—comparable to the bond between hydrogens in Fl2 in bond dissociation energy. 

Alkanes have only -hybridized carbons. The conformation of alkanes is discussed in Chapter 3 (see Section 3.2.2). Methane (CH4) is a nonpolar molecule, and has four covalent carbon-hydrogen bonds. In methane, aU four C—H bonds have the same length (1.10 A), and all the bond angles (109.5°) are the same. Therefore, all four covalent bonds in methane are identical. Three different ways to represent a methane molecule are shown here. In a perspective formula, bonds in the plane of the paper are drawn as solid hues, bonds sticking out of the plane of the paper towards you are... 

Formation of covalent bonds in methane. Carbon needs to share four electrons, in effect it has four slots. Each hydrogen provides an electron to each of these slots. At the same time each hydrogen needs to fill one slot, which is done by sharing an electron with the carbon. 

Normally, atoms of elements in the middle of a period of the periodic table, such as carbon or nitrogen atoms, share electrons to form covalent bonds. In methane, CH4, each of 4 H atoms shares an electron with 1C atom, giving each C atom an 8-electron outer shell (octet) like neon (Figure 4.4). Each H atom has 2 electrons, both shared with C, which provides a shell of 2 electrons like that in the noble gas helium. 

Figure 2.16. Geometry of covalent bonding in methane and polyethylene with all-irani conformation.

The atoms in the molecules of these pain relievers are covalently bonded. Electrons are shared between atoms in a series of single and double covalent bonds. The covalent bonds in aspirin, acetaminophen, and ibuprofen are similar to those found in methane and carbon dioxide. 

The idea here is just the same, except for inevitable refinements and details, for the formation of aU covalent bonds. So the basic ideas for chemical bonding in methane, ammonia, water, and so on, are the same. 

Carbon has four valence electrons. Each electron pairs with an electron from a hydrogen atom in the four covalent bonds of methane. 

Thinking Criticaiiy In a methane molecule (CH4), there are 4 single covalent bonds. In... 

In chemistry, covalent bonds in which two electrons are shared are represented by a single straight line, denoting a single covalent bond. Figure 22-2 shows four different ways to represent a methane molecule. 

A carbon atom can form four covalent bonds. In the simplest hydrocarbon, methane, a single carbon is bonded to four hydrogen atoms. Methane is the main component of the natural gas that you burn when you light a Bunsen burner. The next simplest hydrocarbon, ethane, is formed when two carbon atoms bond to each other as well as to three hydrogen atoms apiece. 

Carbon disulfide is an important solvent for waxes and greases. Methane is the principal component of natural gas. Nitrogen dioxide is used for making nitric acid and is also an atmospheric pollutant. All three compounds contain covalent bonds in which the sharing of electrons is more or less equal. 

A vexing puzzle in the early days of valence bond theory concerned the bonding in methane (CH4). Since covalent bonding requires the overlap of half-filled orbitals of the connected atoms, carbon with an electron configuration of ls 2s 2p 2py has only two half-filled orbitals (Figure 1.20a), so how can it have bonds to four hydrogens ... 

The best way to keep the negative charges for the four covalent bonds in a methane molecule as far apart as possible is to place them in a three-dimensional molecular shape called tetrahedral, with angles of 109.5° between the bonds. 

To explain bonding in methane, VB theory uses hypothetical hybrid orbitals, which are atomic orbitals obtained when two or more nonequivalent orbitals of the same atom combine in preparation for covalent bond formation. Hybridization is the term applied to the mixing of atomic orbitals in an atom (usually a central atom) to generate a set of hybrid orbitals. We can generate four equivalent hybrid orbitals for carbon by mixing the 2s orbital and the three 2p orbitals ... 

Methane (CH4) has four covalent C—H bonds. Because all four bonds have the same length and all the bond angles are the same (109.5°), we can conclude that the four C—H bonds in methane are identical. 

We have managed to account for the observation that carbon forms four covalent bonds, but what accounts for the fact that the four C—H bonds in methane are identical Each has a bond length of 1.10 A, and breaking any one of the bonds requires the same amount of energy (105 kcal/mol, or 439 kJ/mol). If carbon used an s orbital and three p orbitals to form these four bonds, the bond formed with the s orbital would be different from the three bonds formed withp orbitals. How can carbon form four identical bonds, using one 5 and three p orbitals The answer is that carbon uses hybrid orbitals. 

Intepret Data In a methane molecule (CFI4), there are four single covalent bonds. In an octane molecule (CsFlis), there are 25 single covalent bonds. Flow does the number of bonds affect the dispersion forces in samples of methane and octane Which compound is a gas at room temperature Which is a liquid ... 

The hybridization results in one half-filled 2s orbital, and three half-filled 2p orbitals (a total of four half-filled orbitals). These unpaired electrons form the sp hybridized carbon, which can form the four covalent bonds in the methane molecule. The four sp hybrids are directed to the comers of a tetrahedron with bond angles of 109.5°. 

The VSEPR model, simple as it is, does a surprisingly good job at predicting molecular shape, despite the fact that it has no obvious relationship to the filling and shapes of atomic orbitals. For example, we would like to understand how to account for the tetrahedral arrangement of C—H bonds in methane in terms of the 2s and 2p orbitals of the central carbon atom, which are not directed toward the apices of a tetrahedron. How can we reconcile the notion that covalent bonds are formed from overlap of atomic orbitals with the molecular geometries that come from the VSEPR model ... 

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