Molecule monatomic

Argon is frequently used for the determination of surface area, usually at 77 K. Like the other noble gases, argon is of course chemically inert and is composed of spherically symmetrical monatomic molecules. Argon stands in... 

The elements helium, neon, argon, krypton, xenon, and radon—known as the noble gases—almost always have monatomic molecules. Their atoms are not combined with atoms of other elements or with other atoms like themselves. Prior to 1962, no compounds of these elements were known. (Since 1962, some compounds of krypton, xenon, and radon have been prepared.) Why are these elements so stable, while the elements with atomic numbers 1 less or 1 more are so reactive The answer lies in the electronic structures of their atoms. The electrons in atoms are arranged in shells, as described in Sec. 3.6. (A more detailed account of electronic structure will be presented in Chap. 17.)... 

We begin by considering an assembly of N particles and marking the initial momentum and position of each molecule as the set (p (0), r (0)), wherep (O) is a vector of the initial px, Py, Pz) momentum of every particle andr (O) is a vector of the initial (x, y, z) position of every particle. Thus, for a system with N monatomic molecules, the number of variables would be 6N. The equation of motion is usually written in the Hamiltonian form by defining the Hamiltonian as the sum of the potential and the kinetic energies of the particles ... 

Figure 4.18 Entropy of monatomic molecules noble gases...

Gaseous Dissociation.—As with sulphur, determinations of the vapour density of selenium give indications of alteration in the molecular condition, the values up to 900° C. suggesting a mixture mainly of Se6 and Se3 molecules below 550° C. there may be a small proportion of Se8 molecules present, whilst at temperatures above 900° C. it is possible that a few monatomic molecules are formed, but the vapour is then almost entirely composed of Sea molecules.5... 

MOLECULE, hi the traditional sense, a molecule is the smallest particle of a chemical substance capable of independent existence with retention of all its chemical properties. Molecules comprise one or more atoms which need not be of the same kind. Only the rare, or noble gases form single-atom or monatomic molecules. All other elements form bi-. Iri. quudrt-. etc. atomic molecules, e.g.. hydrogen. H ozone. O-, phosphorus. P4 and sulfur, Sx or hydrogen chloride. IICI sodium sullide. Na S. aluminum chloride, AlClu carbon tetrachloride. C CI. and so on. 

The gaseous elements helium, neon, argon, krypton, xenon and radon are composed of separate and individual atoms. When an element exists as separate atoms, then the molecules are said to be monatomic. In chemical shorthand these monatomic molecules are written as He, Ne, Ar, Kr, Xe and Rn respectively. 

Monatomic molecule A molecule which consists of only one atom, for example neon and argon. 

Mercury, with filled 5d and 6s subshells, also has the pseudo noble gas configuration. In the gas phase, Hg exists as a monatomic molecule. From Fig. 2.4.1, Hg has an I value similar to those of noble gases it occupies a maximum position in the h curve. The interaction between mercury atoms is of the van der Waals type. Hence, Hg and Au have some notably different properties ... 

The internal energy of a substance does not include any energy that it may possess as a result of its macroscopic position or movement. Rather it refers to the energy of the molecules making up the substance, which are in ceaseless motion and possess kinetic energy of translation except for monatomic molecules, they also possess kinetic energy of rotation and of internal vibration. The addition of heat to a substance increases this molecular activity, and thus causes an increase in its internal energy. Work done on the substance can have the same effect, as was shown by Joule. 

CCI4, C2H4, and Sg are substances that exist in the form of molecules and thus have molecular masses. Ne can be considered a monatomic molecule, in which case its molecular mass is equal to its atomic mass. All of the substances have molar masses, whether they exist in the form of molecules or not. 

The constant of proportionality a is called the polarisability of the molecule. For isotropic molecules, which include the monatomic molecules of the inert gases, the average direction of the induced molecular dipoles is in the direction of the applied field. (Since the local field is, as we shall see later, proportional to the overall applied field, we have m = const.E.) The total dipole moment per unit volume developed in this way, the polarisation P, is then related to the number of molecules per unit volume Nq . 

Ans. In Problem 12.34, molecules are involved. In Problem 12.32, uncombined atoms are involved. In both cases, the same laws apply, and it is best to regard an uncombined atom of He, for example, as a monatomic molecule. 

In order to illustrate the consequences of equation (70), it will be assumed that the partition functions for the reactants and the complex can be expressed as products of the appropriate numbers of translational, rotational and vibrational partition functions. For simplicity we shall also neglect factors associated with nuclear spin and electronic excitation. If = total number of atoms in a molecule of species i and = 0 for nonlinear molecules, 1 for linear molecules, and 3 for monatomic molecules, then the correct numbers of the various kinds of degrees of freedom are obtained in equation (70) by letting... 

FIG. 3-17. Iodine vapor at elevated temperature this vapor contains both diatomic molecules (U) and monatomic molecules (I) of iodine. 

The first element in the periodic able, hydrogen, is a reactive substance which forms a great many compounds. The c hemistry of hydrogen is discussed in the following chapter. Helium, the second element, is much different it is a gas with the very striking chemical property that it forms no chemical compounds whatever, but exists only in the free state. Its atoms will not even combine witfi one another to form polyatomic molecules, but remain as separate atoms,in the gas, which is hence described as containing monatomic molecules. Because of its property of remaining aloof from other elements it is called a noble gas. 

All molecules exert a weak attraction upon one another. This attraction, the electronic van der Waals attraction, is the result of the mutual interaction of the electrons and nuclei of the molecules it has its origin in the electrostatic attraction of the nuclei of one molecule for the electrons of another, which is largely but not completely compensated by the repulsion of electrons by electrons and nuclei by nuclei. The van der Waals attraction is significant only when the molecules are very close together—almost in contact with one another. For monatomic molecules, such as those of a noble gas, the force of attraction is inversely proportional to the seventh power of the distance between the centers of the molecules, and hence is less than I percent as great wlien the molecules are 10 A apart as when they are 5 A apart. At small distances (about 4 A for argon, for example) the force of attraction is balanced by a force of repulsion due to interpenetration of the outer electron shells of the molecules (Fig. 15-3). 

---