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From Wikipedia

Molecular geometry

Molecular geometry or molecular structure is the three-dimensional arrangement of the atoms that constitute a molecule. It determines several properties of a substance including its reactivity, polarity, phase of matter, color, magnetism, and biological activity.

Molecular geometry determination

The molecular geometry can be determined by various spectroscopic methods and diffraction methods. IR, microwave and Raman spectroscopy can give information about the molecule geometry from the details of the vibrational and rotational absorbances detected by these techniques. X-ray crystallography, neutron diffraction and electron diffraction can give molecular structure for crystalline solids based on the distance between nuclei and concentration of electron density. Gas electron diffraction can be used for small molecules in the gas phase. NMR and FRET methods can be used to determine complementary information including relative distances,

dihedral angles,

angles, and connectivity. Molecular geometries are best determined at low temperature because at higher temperatures the molecular structure is averaged over more accessible geometries (see next section). Larger molecules often exist in multiple stable geometries (conformational isomerism) that are close in energy on the potential energy surface. Geometries can also be computed by ab initio quantum chemistry methods to high accuracy. The molecular geometry can be different as a solid, in solution, and as a gas.

The position of each atom is determined by the nature of the chemical bonds by which it is connected to its neighboring atoms. The molecular geometry can be described by the positions of these atoms in space, evoking bond lengths of two joined atoms, bond angles of three connected atoms, and torsion angles (dihedral angles) of three consecutive bonds.

The influence of thermal excitation

Since the motions of the atoms in a molecule are determined by quantum mechanics, one must define “motion� in a quantum mechanical way. The overall (external) quantum mechanical motions translation and rotation hardly change the geometry of the molecule. (To some extent rotation influences the geometry via Coriolis forces and centrifugal distortion, but this is negligible for the present discussion.) A third type of motion is vibration, which is the internal motion of the atoms in a molecule. The molecular vibrations are harmonic (at least to good approximation), which means that the atoms oscillate about their equilibrium, even at the absolute zero of temperature. At absolute zero all atoms are in their vibrational ground state and show zero point quantum mechanical motion, that is, the wavefunction of a single vibrational mode is not a sharp peak, but an exponential of finite width. At higher temperatures the vibrational modes may be thermally excited (in a classical interpretation one expresses this by stating that “the molecules will vibrate faster�), but they oscillate still around the recognizable geometry of the molecule.

To get a feeling for the probability that the vibration of molecule may be thermally excited, we inspect the Boltzmann factor \exp\left( -\frac{\Delta E}{kT} \right) , where \Delta E is the excitation energy of the vibrational mode, k the Boltzmann constant and T the absolute temperature. At 298K (25 Â°C), typical values for the Boltzmann factor are: 0.089 for ΔE = 500 cm−1 ; ΔE = 0.008 for 1000 cm−1 ; 7 10−4 for ΔE = 1500 cm−1. That is, if the excitation energy is 500 cm−1, then about 9 percent of the molecules are thermally excited at room temperature. The lowest excitation vibrational energy in water is the bending mode (about 1600 cm−1). Thus, at room temperature less than 0.07 percent of all the molecules of a given amount of water will vibrate faster than at absolute zero.

As stated above, rotation hardly influences the molecular geometry. But, as a quantum mechanical motion, it is thermally excited at relatively (as compared to vibration) low temperatures. From a classical point of view it can be stated that more molecules rotate faster at higher temperatures, i.e., they have larger angular velocity and angular momentum. In quantum mechanically language: more eigenstates of higher angular momentum become thermally populated with rising temperatures. Typical rotational excitation energies are on the order of a few cm−1.

The results of many spectroscopic experiments are broadened because they involve an averaging over rotational states. It is often difficult to extract geometries from spectra at high temperatures, because the number of rotational states probed in the experimental averaging increases with increasing temperature. Thus, many spectroscopic observations can only be expected to yield reliable molecular geometries at temperatures close to absolute zero, because at higher temperatures too many higher rotational states are thermally populated.


Molecules, by definition, are most often held together with covalent bonds involving single, double, and/or triple bonds, where a "bond" is a shared pair of electrons (the other method of

Judgment as a matter of law - Wikipedia, the free encyclopedia

Judgment as a matter of law (JMOL) is a motion made by a party, during trial, claiming the opposing party has insufficient evidence to reasonably support ...

From Encyclopedia

Molecular Structure Molecular Structure

Throughout history, humans have created models to help them explain the observed character of substances and phenomena in the material world. The ancient philosophers Democritus and Lucretius were among the first to speculate that matter was discontinuous, and that small, indivisible particles not only made up substances but also gave them their observed properties. The Greeks called these particles "atoms" (the English equivalent), a word that meant indivisible. Lucretius imagined that the particles that made up vapor had smooth surfaces and could not interconnect, giving vapors (gases) their extreme mobility. Liquids, on the other hand, were thought to be made up of particles, each particle having a few hooks. These few hooks would get entwined but would not immobilize the particles, thereby causing the particles to cling, yet still be fluid. The particles that made up solids, by contrast, were thought to have many hooks, resulting in the extremely sturdy nature of solid materials. The hypothesis of finite particles implied empty space between them. Yet, the majority of Greek philosophers did not believe that nothingness (the vacuums between particles) could exist, so the idea of atoms did not last long in the ancient times. Ironically, the objection was not to the existence of particles, but to the vacancies that must exist between them. Most cultures have linked properties of matter with religious and/or superstitious ideas. The term "gold" derives from an Old English word meaning "something shiny and yellow like the Sun"; it served not only as the name of the metal but also identified its properties. Polished gold nearly captures the sunlight it reflects, and the astronomical, astrological, medical, and religious attributes of the Sun were thought to be present in gold metal. For thousands of years, substances were said to contain essences or essential parts that gave them their characters. In a sense modern ideas about molecular structure do something similar. Chemists construct explanations for observed, macroscopic phenomena (e.g., reactivity) by describing the assemblages, shapes, and motions of submicroscopic particles. The theory of atoms did not reemerge until the seventeenth century. The discovery of elements rapidly led to the idea that nonelementary substances were made up of molecules that were, in turn, collections of elemental atoms. During the first years of chemical analyses, different substances were observed to have different compositions; the deduction was made that substances were different because their compositions were different. One type of mineral might be 34 percent iron and 66 percent oxygen. Each sample of that mineral would give the same results (34% iron and 66% oxygen). A different mineral, that is, one with different properties, might be 56 percent iron and 44 percent oxygen. Although there was still no concept of bonding between atoms or of molecular geometry at the beginning of the nineteenth century, chemists had developed the idea that different molecules were different collections of atoms. Scientific theories are sometimes discarded. When information that contradicts a theory is reliable, the theory must be changed to fit the new data. As the elemental analysis of compounds expanded greatly during the early 1800s, observations that different substances were of the same elemental composition were inevitable. In his History of Chemistry (1830), Thomas Thomson drew illustrations of varying hypothetical particle arrangements, using symbols that were used at that time (those of John Dalton), as a way to explain why two acids of the same elemental composition could have different physical and chemical properties (see Figure 1). These are believed to be the earliest recorded representations of molecular structure that showed varying arrangements of the same atoms; the phenomenon would soon be called isomerism (from the Greek iso, meaning same, and meros, meaning part). In 1828 Friedrich Wöhler (1800–1882) synthesized urea, (NH2)2C = O or CH4N2O, that was indistinguishable from that that had been isolated from urine. He prepared this organic substance from the clearly inorganic (mineralogical) starting material ammonium cyanate, NH4(+) NCO(−), also CH4N2O, the result of the combination of ammonium chloride and silver cyanate. Urea and ammonium cyanate are constitutional isomers , and together illustrate the fact that fixed arrangements of atoms, molecular structures, must be invoked to explain observed phenomena. The constitution of a molecule (number of, kind of, and connectivities of atoms) may be represented by a two-dimensional "map" in which the interatomic linkages (bonds) are drawn as lines. There are two constitutional isomers that are represented by the molecular formula C2H6O: ethanol and dimethyl ether. The differences in connectivities, which are not evident in the common constitutional inventory C2H6O, can be conveyed by typographical line formulas (CH3CH2OH for ethanol and CH3OCH3 for dimethyl ether), or by structural representations (see Figure 2). As the number and kinds of atoms in substances increase, the number of constitutional isomers increases. By the mid-1850s, a new theory of molecular structure had emerged. Given a unique collection of atoms, it was not the identities of the atoms that distinguished one molecule from another, but rather the connectivity, or bonding, of those atoms. The nature of the chemical bond was unknown, and the phenomenon of chemical bonding was described as "chemical affinity." Because it was observed that the passing of electricity through some substances, such as water, could "break" the molecules apart into their elements (electrolysis), the electrostatic attractions of charged particles (ions) were used to contribute to an explanation of chemical affinity. Just as the hypothesis of the varying connectivities of atoms emerged as a response to observations that could not be explained, variation in the three-dimensional arrangements of atoms in space was proposed to reconcile other observed phenomena. Jacobus van't Hoff (1852–1911) and Joseph-Achille Le Bel (1847–1930) proposed (independently of one another, in 1874) that molecules of the same connectivity yet different physical properties (e.g., optical activity) might be explained if, in the case of four different particles, the arrangement (configuration) of the particles was tetrahedral. Macroscopically or microscopically, a tetrahedral array of four different things gives rise to two and only two different arrangements that are nonsuperimposable mirror images (enantiomers; see Figure 3). Distinct molecular structural units that have the same connectivities but varying three-dimensional arrangements are also isomers. The term "stereoisomer" was introduced by Viktor Meyer in 1888 to describe molecules that differ only in their three-dimensional arrangements. Connectivity and stereoisomerism give chemists a way to uniquely differentiate one molecular structure from another. The molecular formula C4H9Br, for instance, represents five different substances (see Figure 4). Predictably, although there is only one compound for each of the connectivities designated 1-bromobutane, 2-bromo-2-methylpropane, and 1-bromo-2-methylpropane, there are two compounds represented by the connectivity designated 2-bromobutane (carbon 2 has four different groups attached, and thus two three-dimensional arrangements of the molecule, whose geometries are labeled R and S, exist). There are no other isomers of C4H9Br that are predicted, and none that are observed. Although the arrangement of molecular atoms around a given point is fixed, molecules are not static objects. The sequence of links in a chain, for instance, is constant, but the chain can be twisted and knotted into countless shapes. In the case of a molecule, twists do not affect the identity of a substance, but the overall molecular shape is part of molecular structure and can have an impact on the observed properties. According to Ernest Eliel and Samuel Wilen (1994, p. 102), configurational stereoisomers result from "arrangements of atoms in space of a mo

From Yahoo Answers

Question:Suggest how Brownian motion can be used as evidence to suppprt the particle model. This is about the particles in a matter.

Answers:Because it can be interpreted (and happens to be the right assumption) as the collective effect of small amounts of momentum transfer from atoms and molecules to a mesoscopic particle of dust suspended in the air for example. Einstein was the first to give this interpretation in 1905 to infer the existence of atoms and molecules.


Answers:lol. i'm looking for it aswell for my science exam :| (: this is the most i could find on it from the internet... The kinetic-molecular theory states: 1) All matter is composed of very small particles called atoms,ions or molecules. 2) All of these small particles are in constant motion, even at the coldest temperature whether vibratory or translatory. 3) The kinetic energy of the particles is a measure of temperature. The greater the number of impacts the greater will be the pressure and vice-versa. 4) These particles collide but the total energy remains same and this is from my school notes >> everything is made up of molecules in motion >> they must collide in order to react >> they must collide with a minimum in order to react i don't really know how it relates to anything :| sorry! goodluck! (:

Question:It is agreed on all sides that there are only two possible solutions to the riddle of origins. Either Someone made the world, or the world made itself. A third option, the world is eternal and without origin, contradicts Natural Laws such as Thermodynamics and has been disproved with mathematical certainty in the 20th century. As the universe is obviously complex and seemingly well-designed, a Designer should be the scientific default. In everything we observe today, concept and design are the result of a Mind. Furthermore, Natural Laws such as Gravity, Inverse Squares, Cause and Effect, and Thermodynamics imply a Law-giver. Unless a natural mechanism constrained by Natural Law, by which the entire universe could come into existence and further develop through random process, is found, a Creator must be the theoretical default. Please ignore this question and additional details. This is merely a test to see who takes the time to read the addition details in questions posted on this forum. If you have read these details, please include the word "bandito" in your answer. Once again, this has been a test, and no serious reponse is needed or necessary. I will now return you to your originally scheduled program. It doesn't matter whether an individual scientist has difficulty accepting it or not. As Sir Arthur Conan Doyle so eloquently stated in his Sherlock Holmes series, "Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth." Creation Evidence - A Few Brief Examples: Lack of Transitional Fossils. Charles Darwin wrote, "Lastly, looking not to any one time, but to all time, if my theory be true, numberless intermediate varieties, linking closely together all the species of the same group, must assuredly have existed. But, as by this theory, innumerable transitional forms must have existed, why do we not find them embedded in countless numbers in the crust of the earth?" (Origin of Species, 1859). Since Darwin put forth his theory, scientists have sought fossil evidence indicating past organic transitions. Nearly 150 years later, there has been no evidence of transition found thus far in the fossil record. Lack of a Natural Mechanism. Charles Darwin, in his Origin of Species, proposed Natural Selection to be the mechanism by which an original simple-celled organism could have evolved gradually into all species observed today, both plant and animal. Darwin defines evolution as "descent with modification." However, Natural Selection is known to be a conservative process, not a means of developing complexity from simplicity. Later, with our increased understanding of genetics, it was thought perhaps Natural Selection in conjunction with genetic mutation allowed for the development of all species from a common ancestor. However, this is theoretical and controversial, since "beneficial" mutations have yet to be observed. In fact, scientists have only observed harmful, "downward" mutations thus far. Time Constraints. Both Creationists and Evolutionists agree that if evolution is at all possible, there needs to be an excessive (if not infinite) amount of time. For much of the 20th century, it was thought evolutionists had all the time they needed. If the earth ever looked too young for certain evolutionary developments to have occurred, the age was pushed back in the textbooks. In 1905, the earth was declared to be two billion years old. By 1970, the earth was determined to be 3.5 billion years old, and by the 1990's, the earth had become 4.6 billion years old. However, Young Earth advocates have identified quite a few Young Earth chronometers in recent years. Currently, there are approximately five times more natural chronometers indicating a "Young Earth" than an "Old Earth." Each discovery is a separate "Limiting Factor" that places a constraint on the possible age of the earth. For example, moon drift, earth rotation speed, magnetic field decay, erosion rates, chemical influx into the oceans, ocean salinity, etc, all constrain the possible age of the earth. Each Limiting Factor is distinct. If one were successfully challenged, there is still the problem of all the rest. Furthermore, there are Limiting Factors constraining the possible age of the universe, such as spiral galaxies where they're maintaining their spiral shapes despite their centers spinning faster than their extremities. Unacceptable Model of Origins. The Big Bang Theory is the accepted source of Origins among the majority of Evolutionists, and is taught in our public schools. However, the Big Bang does not explain many things, including the uneven distribution of matter that results in "voids" and "clumps," or the retrograde motion that must violate the Law of Conservation of Angular Momentum. Furthermore, the Big Bang does not address the primary question at hand, "where did everything come from?" Did nothing explode? How did this explosion cause order, while every explosion observed in r pab - "so many things are wrong with that giant wall of text" ... are there? I have a feeling you didn't read it :-P

Answers:I like your style you naughty bandito. You've picked up on a very common problem on this site. Lazy people prefer 'sound bites' rather than studying and thinking about a reasoned question before answering.

Question:example of these situations that I need is in the study in solid, for example: the possibility of water to fill the empty spaces between tightly compact pebbles on a container which is an evidence of solid molecular spaces.How about in liquid?gas?plasma?

Answers:You can use "compression" to show that gases have space between the molecules Gases are readily compressible. But solids and liquids are not very compressible at all, indicating that there is little to no space between the molecules of solids and liquids. The problem here is what we define as "spaces" between molecules. Think of molecules as marbles. Lay out some marbles on the floor with a minimum of 5 cm between them. In this case there is space between the marbles. This would be analogous to a gas. Now bring the marbles together so that they are touching but not in a regular pattern. This is analogous to a liquid. Notice that there are spaces between the round marbles, but not much. Not enough to stick another marble in in most cases. Now arrange the marbles in a regular pattern to represent a solid. Notice that there are only tiny spaces between the round marbles which would not accommodate another marble. Lack of compressibility negates your assumption that solids and liquids have spaces between the molecules. The bit with out the water filling the interstitial spaces between pebbles does not apply at the molecular level. Here is one more bit of evidence. Suppose you dissolve an ionic solid in water. If there were lots of space between the water molecules then the ions would fill the spaces and the volume of water would not change. Instead, dissolving a solid in water will increase the volume of the solution, indicating that there was little to no "empty space" between the water molecules. ========= Follow up ========= AlienXXX's example of thermal expansion shows that there are NOT spaces between the atoms/molecules in a solid. If there were spaces then when there was increased motion due to the elevated temperature the molecules would simply vibrate within the empty space and not change the volume or length of the material. The fact that the substance does expand shows that there was NOT empty spaces between the particles of the solid. As the molecules move around more the substance must expand to accommodate this increased molecular motion.

From Youtube

Experimental evidence for the space matter in an atom :In an isolated- non-radioactive atom, there are two types of forces acting on its electrons. They are attraction from the nucleus and repulsion between electrons (in hydrogen atom, attraction from the nucleus only). But, these forces cannot create constant motion in electrons and so the current theory of atom is simply wrong. Volume of atoms and elastic nature of atoms [for example, 1. gas atoms move randomly in high speed and bounce back when they collide with other atoms or its container, 2. the capacity of a material to store thermal energy (oscillation and collision between atoms)] indicate that the nucleus of an atom is surrounded by a form of elastic matter. I name this matter as space matter. An experiment for detecting space matter that released in a chemical reaction: When the combustion is taking place in the combustion container, the space matter that released in the reaction will be filled in the space matter collector and flows to the refraction box through the space matter channel. When a light beam is passed through this space matter flow, a shadow effect (shadowgraph) is obtained. Watch my other videos: Structure of the atom, structure of a charged particle, electric field and magnetic field, how is light emitted, light is oscillating magnetic line, nuclear energy, uncertainty principle is wrong, no standing waves and matter waves, etc. List of related videos: The space inside of atom is not empty, but filled with space matter. Experimental evidence for ...

Forms Of Matter :Check us out at www.tutorvista.com States of matter are the distinct forms that different phases of matter take on. Historically, the distinction is made based on qualitative differences in bulk properties. Solid is the state in which matter maintains a fixed volume and shape; liquid is the state in which matter maintains a fixed volume but adapts to the shape of its container; and gas is the state in which matter expands to occupy whatever volume is available. More recently, distinctions between states have been based on differences in molecular interrelationships. Solid is the state in which intermolecular attractions keep the molecules in fixed spatial relationships. Liquid is the state in which intermolecular attractions keep molecules in proximity, but do not keep the molecules in fixed relationships. Gas is that state in which the molecules are comparatively separated and intermolecular attractions have relatively little effect on their respective motions. Plasma is a highly ionized gas that occurs at high temperatures. The intermolecular forces created by ionic attractions and repulsions give these compositions distinct properties, for which reason plasma is described as a fourth state of matter. Solid The particles (ions, atoms or molecules) are packed closely together. The forces between particles are strong enough so that the particles cannot move freely but can only vibrate. As a result, a solid has a stable, definite shape, and a definite volume. Solids can ...