Mass, atomic/molecular

A suitable mass spectrometer can be set to measure relative atomic, molecular, or fragment ion mass. 

It is very evident in Figure 3 that the chemical complexity of Hasteloy presents special problems for mass spectrometric analysis using a quadrupole mass spectrometer with low mass resolution. Molecular ions comprised of combinations of matrix and plasma atoms are formed in abundance and will obscure many elements... 

One mole of O2 molecules contains two moles of O atoms, so the molar mass of molecular O2 is calculated as... 

The Periodic Table forms one of the most remarkable, concise, and valuable tabulations of data in science. Its power lies in the regularities that it reveals, thus, in some respects, it has the same role as the SOM. Construct a SOM in which the input consists of a few properties of some elements, such as electronegativity, atomic mass, atomic radius, and electron affinity. Does the completed map show the kind of clustering of elements that you would expect What is the effect of varying the weight given to the different molecular properties that you are using ... 

Strictly speaking, the terms molar mass and molecular weight refer to different quantities. Molar mass is the mass of one mole of polymer molecules and measured in g/mol, whereas molecular weight is dimensionless and refers to the weight (mass) of a single polymer molecule measured as multiples of the atomic mass unit u. The numerical values of both quantities are identical. Usually, no such strict distinction is made in the literature, and also in this contribution both terms will be used as synonyms for the strict term molar mass. 

The interaction of two harmonic oscillators with spring constants = k, and masses = m, separated by a distance = r is to be considered. Each atomic (molecular) oscillator has a frequency, v = ( /2n)J(k/m). Their orientations are assumed to be collinear (Figure 3.11). 

A mole is also the formula (atomic, molecular) mass expressed in grams. 

Mass spectrometers use the difference in mass-to-charge ratio (m/z) of ionized atoms, molecular fragments, or whole molecules to differentiate between them. Mass spectrometry is therefore useful for quantitation of atoms or molecules and also for determining chemical and structural information about them [329, 531-533]. Molecules have distinctive fragmentation patterns which provide information to identify structural components. The general operation of a mass spectrometer is to (1) create gas-phase ions, (2) separate the ions in space or time based on their mass-to-charge ratio, and (3) measure the quantity of ions of each mass-to-charge ratio. The ion separation power of a mass spectrometer is described by the resolution, which is defined as ... 

In Chapter 3, a formula was presented which connects the normal vibrational frequencies of two rigid-rotor-harmonic-oscillator isotopomers with their respective atomic masses m , molecular masses Mi and moments of inertia (the Teller-Redlich product rule). If this identity is substituted into Equation 4.77, one obtains... 

Effects of isotopic mass on molecular and atomic velocities and diffiisivity... 

Molar mass M molecular weight in atomic mass units (amu)... 

Legionella pneumophila produces a siderophore named legiobactin, which shows no catecholate or hydroxamate reactions (206). Enzymatic studies suggest a citrate structure in agreement with the data obtained by mass spectrometry (molecular mass ca. 350 Da) and NMR (three carbonyl and ten aliphatic C atoms). It is not clear yet as to whether legiobactin is essential for the iron acquisition in the aqueous habitat of the bacterium or during lung infection (2, 65). 

Chemists may distinguish between the molar masses of pure elements, molecular compounds, and ionic compounds by referring to them as the gram atomic mass, gram molecular mass, and gram formula mass, respectively. Don t be fooled The basic concept behind each term is the same molar mass. 

The nitrogen rule helps us propose compositions for molecular ions If a compound has an odd number of nitrogen atoms—in addition to any number of C, H, halogens, O, S, Si, and P—then M+ has an odd nominal mass. For a compound with an even number of nitrogen atoms (0, 2, 4, and so on), M+ has an even nominal mass. A molecular ion at mlz 128 can have 0 or 2 N atoms, but it cannot have 1 N atom. 

The molar masses of molecular and ionic compounds are calculated from the molar masses of the elements present the molar mass of a compound is the sum of the molar masses of the elements that make up the molecule or the formula unit. We need only note how many times each atom or ion appears in the molecular formula or the formula unit of the ionic compound. For example, the molar mass of the ionic compound Na2S04 is... 

A hydrocarbon of empirical formula C2H3 took 349 s to effuse through a porous plug. Under the same conditions of temperature and pressure, it took 210 s for the same amount of argon atoms to effuse. What is the molar mass and molecular formula of the hydrocarbon ... 

Just as atomic mass is the mass of an atom, molecular mass is the mass of a molecule. The analogous term formula mass is used for ionic and other nonmolecular substances. Molecular mass is the sum of the atomic masses of all atoms in the molecule. When referring to the large numbers of molecules or ions that take part in a visible chemical reaction, it s convenient to use a unit called the mole, abbreviated mol. One mole of any object, atom, molecule, or ion contains Avogadro s number of formula units, 6.022 x 1023. 

Macroscopic stick-slip motion described above applies to the center of mass movement of the bodies. However, even in situations where the movement of the overall mass is smooth and steady, there may occur local, microscopic stick-slip. This involves the movement of single atoms, molecular groups, or asperities. In fact, such stick-slip events form the basis of microscopic models of friction and are the explanation why the friction force is largely independent of speed (see Section 11.1.9). 

The dalton is not accepted within SI [9], It is perceived as a molecular mass of a specific species. In protocols, molar mass, relative molecular mass or unified atomic mass units should be substituted. The last of these, in conjunction with the SI mass unit, is currently acceptable with an added relative standard uncertainty of 10 6-... 

Refer to the periodic table for the appropriate atomic masses. The molecular masses are calculated using the... 

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