Atomic structure modern view

Modem views of atomic structure are, as we have seen, based largely on the applications of wave mechanics to atomic systems. Modern views of molecular structure are based on applying wave mechanics to molecules such studies provide answers as to how and why atoms combine. The Schrodinger equation can be written to describe the behaviour of electrons in molecules, but it can be solved only approximately. Two such methods are the valence bond approach, developed by Heitler and Pauling, and the molecular orbital approach associated with Hund and MuUiken ... 

The Rutherford Experiment movie (eChapter 2.4) shows alpha particles impinging on a thin gold foil. Describe what happens to the alpha particles and discuss how the results of this experiment shaped the modern view of atomic structure. 

The anomeric effect in terms of a stabilizing effect can be illustrated by the concept of "double-bond - no-bond resonance" (14, 15) shown by the resonance structures 4 and 2 or by the equivalent modern view (16, 17) that this electronic delocalization is due to the overlap of an electron pair orbital of an oxygen atom with the antibonding orbital of a C —OR sigma bond (12). 

The modern view of the periodic table explains its structure in terms of an Aufbau procedure based on the wave-mechanical model of the hydrogen atom. Although seductive at first glance, the model is totally inadequate to account for details of the observed electronic configurations of atoms, and makes no distinction between isotopes of the same element. The attractive part of the wave-mechanical model is that it predicts a periodic sequence of electronic configurations readily specified as a function of atomic number. The periodicity follows from the progressive increase of four quantum numbers n, l, mi and s, such that... 

MODERN VIEW OF ATOMIC STRUCTURE ATOMIC WEIGHTS (sections 2.3-2.4)... 

The science of thermodynamics developed as a means of describing the properties of matter in our macroscopic world without regard to microscopic structure. In fact, thermodynamics was a well-developed field before the modern view of atomic and molecular structure was even known. The thermodynamic properties of water, for example, addressed the behavior of bulk water (or ice or water vapor) as a substance without considering any specific properties of individual H2O molecules. 

Prior to Rutherford s gold-foil experiment, the mass and positively charged particles of an atom were thought to be evenly distributed throughout the volume of the atom, (a) Watch the movie of the Rutherford Experiment (eChapter 2.2), and describe how the experimental results would have been different if the earlier model had been correct, (b) What specific feature of the modern view of atomic structure was illuminated by Rutherford s experiment ... 

Many biochemical structures, including DNA, are in part made up of derivatives of phosphoric acid. These derivatives are referred to as phosphoesters. The P atoms in these structures are nearly always depicted with five bonds. However, as just described, the modern view of such structures involves charge separation and sp hybridization at P. Because the five-bond representation is historically the most widely spread depiction, this depiction is how we render such struc-... 

As discussed in Paresegian s recent book, the modern view of dispersion interactions has its roots in the the Casimir effect. " Rather than charge fluctuations, the phenomenon can be viewed in terms of zero-point electromagnetic-field fluctuations in the vacuum as allowed by the Heisenberg uncertainty principle (AEAt>b/ln). Atoms and molecules can absorb some of these frequencies, namely those frequencies that are resonant with transitions between the quantum mechanical energy levels of the system as determined by its electronic structure. This absorption of the electromagnetic fluctuations gives rise to attractive forces between two bodies. 

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