Atoms empty space

Figure C3.2.16. Dependence of measured resistance in an STM junction consisting of a bare tip a tip with one Xe atom attached, and a tip with two Xe atoms. Note that the Xe atoms facilitate tunnelling (compared to empty space). From Yazdani A, Eigler D M and Lang N D 1996 Off resonance conduction tlirough atomic wires Science 111 1921-4.

The molar volume is usually larger than the van der Waals volume because two additional influences must be added. The first is the amount of empty space in the bulk material due to constraints on how tightly together the chains can pack. The second is the additional space needed to accommodate the vibrational motion of the atoms at a given temperature. 

In addition to chemical or physical properties, a fascinating aspect of fullerene related materials is their central empty space, where atoms, molecules or particles can be enclosed. The enclosed particles are then protected by the robust graphitic layers from chemical or mechanical effects. The very long cavities of CNTs have a special potential due to their high aspect ratio and they can be used as templates to fabricate elongated nanostructures. 

FIGURE 1.6 Rutherford s model of the atom explains why most u particles pass almost straight through the platinum foil, whereas a very few—those scoring a direct hit on the nucleus—undergo verv large deflections. Most of the atom is nearly empty space thinly populated by the atom s electrons. The nuclei are much smaller relative to their atoms than shown here. 

Krypton crystallizes with a face-centered cubic unit cell of edge 559 pm. (a) What is the density of solid krypton (b) What is the atomic radius of krypton (c) What is the volume of one krypton atom (d) What percentage of the unit cell is empty space if each atom is treated as a hard sphere ... 

Whether the Bohr atomic model or the quantum mechanical model is introduced to students, it is inevitable that they have to learn, among other things, that (i) the atomic nucleus is surrounded by electrons and (ii) most of an atom is empty space. Students understanding of the visual representation of the above two statements was explored by Harrison and Treagust (1996). In the study, 48 Grade 8-10... 

In this section, we present some parallels to Aristotehan thinking. Aristotle strongly attacked the idea of atomism. For example, the idea of empty space between... 

In summary, for Leukipp and Demokrit, the empty space between the atoms was a key assumption in their model, because, if particles were closely packed, they could not move and substances could not be mixed. When asking students to philosophise about the nature of matter, we indeed find parallels to the ancient Greek thinking, both to the so-called atomists and to the continuous ideas of Aristotle and others. For example, Leukipp s and Demokrit s explanation for the specific weight of substances corresponds to one student conception younger students especially tend to explain differences in the specific weight (but also hardness of substances) with differences in the closeness of particles (Fig. 10.6). They seldom take into account that the particles could have a different weight themselves. 

This argumentation was strongly attacked by Aristotle who said that water can also move and flow without observable empty spaces in it. Maybe Aristotle simply overestimated the size of atoms as thought by Leukipp and Demokrit (Home, 1975). To justify his denial of empty spaces between atoms, one student said Well, you can t see open spaces in water (Lee et al., 1993, p. 257). Such misleading ideas about the size of atoms and particles are reported for students, too (e.g. Lee et al., 1993). Hence, learning difficulties can be explained by this frame When expecting that particles should be observable but no such particles can be seen, why should a learner believe in the existence of atoms ... 

As the results of Pfundt (1981), Griffith (1987) and Lee et al. (1993) show, students have problems in dealing with the idea of empty spaces between particles. In her studies, Pfundt presented students with different representations of atoms. The students had to choose the one that represented their ideas at best. Numerous students chose representations of cubic or hexagonal atoms, because they fit without gaps between them (Pfundt, 1981, p. 87). Griffith and Preston (1992) could explicitly show that students suppose that the size of a crystal corresponded to the shape of its atoms. Furthermore, they discuss the parallels between this students conception and the corresponding historical idea of Rene Hairy. 

A solid is most stable when each atom, molecule, or ion has as many close neighbors as possible, thus maximizing intermolecular attractions. An arrangement that accomplishes this is described as a close-packed stmcture. Close-packed structures are arranged so that the empty space around the atoms or molecules is minimized. 

If the lattices are viewed as close-packed spheres, the fee and the hep lattices have the highest density, possessing about 26% empty space. Each atom in the interior has 12 nearest neighbors, or in other words, an atom in the interior has a coordination number of 12. The bcc lattice is slightly more open and contains about 32% empty space. The coordination number of a bulk atom inside the bcc lattice is 8. 

Atoms are mostly empty space with small, dense, positively charged centers. 

Explain on the basis of the information in Table 3-2 (a) why the nucleus is positively charged, (ft) why the nucleus contains most of the mass of the atom, (c) why electrons are attracted to the nucleus. (d) why the atom may be considered mostly empty space. 

Ans. (a) The only positively charged particles, the protons, arc located there, (b) The protons and neutrons, both massive compared to the electrons, arc located there, (c) The nucleus is positively charged and they are negatively charged, (d) The nucleus is tiny compared to the atom as a whole, and it contains most of the mass of the atom. Thus, the remainder of the atom contains little mass, and may be thought of as mostly empty space. 

For the Cu tetrahedra to lit into the empty spaces of the Mg pattern there must be a significant difference in the atomic diameters. In this case, the diameter ratio of the pure metals is about 3.2/2.56 = 1.25 which is just enough. Figure 8.3 is a schematic of the complete unit cell. This stmcture is often described in terms of layers lying normal to the (111) directions, but the present method is preferred by this author. 

Nothing exists except atoms and empty space everything else is opinion... 

Empty space in which there are no atoms or molecules. A perfect vacuum cannot be attained in practice and the term denotes a space containing air or other gas at a very low pressure. In industry vacuum is measured in inches of mercury (in Hg) ranging from 0 in at atmospheric pressure to around 30 in at zero absolute pressure. Vacuum Extrusion... 

Rutherford s experiment demonstrated that the total positive charge in an atom is localized in a very small region of space (the nucleus). The majority of a particles simply passed through the gold foil, indicating that they did not come near a nucleus. In other words, most of the atom is empty space. The diffuse cloud of electrons (which has a size on the order of 10 8cm) did not exert enough force on the a particles to deflect them. The plum pudding model simply did not explain the observations from the experiment with a particles. 

We can determine the amount of empty space in the simple cubic (a space-filling model is shown in Figure 7.15) structure by considering it to have an edge length l, which will be twice the radius of an atom. Therefore, the radius of the atom is 1/2, so the volume of one atom is (4/3)7r(l/2)3 = 0.52413, but the volume of the cube is P. From this we see that because the cube contains only one atom that occupies 52.4% of the volume of the cube, there is 47.6% empty space. Because of the low coordination number and the large amount of empty space, the simple cubic structure does not represent an efficient use of space and does not maximize the number of metal atoms bonded to each other. Consequently, the simple cubic structure is not a common one for metals. 

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