Lithium atomic mass

Step 2 To determine the limiting reactant, we must convert the masses of lithium (atomic mass = 6.941 g) and nitrogen (molar mass = 28.02 g) to moles. 

For organometailic compounds, the situation becomes even more complicated because the presence of elements such as platinum, iron, and copper introduces more complex isotopic patterns. In a very general sense, for inorganic chemistry, as atomic number increases, the number of isotopes occurring naturally for any one element can increase considerably. An element of small atomic number, lithium, has only two natural isotopes, but tin has ten, xenon has nine, and mercury has seven isotopes. This general phenomenon should be approached with caution because, for example, yttrium of atomic mass 89 is monoisotopic, and iridium has just two natural isotopes at masses 191 and 193. Nevertheless, the occurrence and variation in patterns of multi-isotopic elements often make their mass spectrometric identification easy, as depicted for the cases of dimethylmercury and dimethylplatinum in Figure 47.4. 

Suppose that Si-28 ( Si) is taken as the standard for expressing atomic masses and assigned an atomic mass of 10.00 amu. Estimate the molar mass of lithium nitride. 

List the number and kind of fundamental particles found in a neutral lithium atom that has a nucleus with a nuclear charge three times that of a hydrogen nucleus and with seven times the mass. 

Extremely stringent lower limits were reported by Rank (29) in 1968. A spectroscopic detection of the Lyman a(2 p - 1 s) emission line of the quarkonium atom (u-quark plus electron) at 2733 A was expected to be able to show less than 3 108 positive quarks, to be compared with 1010 lithium atoms detected by 2 p - 2 s emission at 6708 A. With certain assumptions (the reader is referred to the original article), less than one quark was found per 1018 nucleons in sea water and 1017 nucleons in seaweed, plankton and oysters. Classical oil-drop experiments (with four kinds of oil light mineral, soya-bean, peanut and cod-liver) were interpreted as less than one quark per 1020 nucleons. Whereas a recent value (18) for deep ocean sediments was below 10 21 per nucleon, much more severe limits were reported (30) in 1966 for sea water (quark/nucleon ratio below 3 10-29) and air (below 5 10-27) with certain assumptions about concentration before entrance in the mass spectrometer. At the same time, the ratio was shown to be below 10 17 for a meteorite. Cook etal. (31) attempted to concentrate quarks by ion-exchange columns in aqueous solution, assuming a position of elution between Na+ and Li+. As discussed in the next section, cations with charge + 2/3 may be more similar to Cs+. Anyhow, values below 10 23 for the quark to nucleon ratio were found for several rocks (e.g., volcanic lava) and minerals. It is clear that if such values below a quark per gramme are accurate, we have a very hard time to find the object but it needs a considerably sophisticated technique to be certain that available quarks are not lost before detection. 

As the weak interaction is the slowest of all, it was the first to find itself unable to keep up with the rapid expansion of the Universe. The neutrinos it produces, which serve as an indicator of the weak interaction, were the first to experience decoupling, the particle equivalent of social exclusion. By the first second, expansion-cooled neutrinos ceased to interact with other matter in the form of protons and neutrons. This left the latter free to organise themselves into nuclei. Indeed, fertile reactions soon got under way between protons and neutrons. However, the instability of species with atomic masses between 5 and 8 quickly put paid to this first attempt at nuclear architecture. The two species of nucleon, protons and neutrons, were distributed over a narrow range of nuclei from hydrogen to lithium-7, but in a quite unequal way. 

As the number of elements increased, so did attempts to organize them into meaningful relationships. Johann Dobereiner (1780-1849) discovered in 1829 that certain elements had atomic masses and properties that fell approximately mid-way between the masses and properties of two other elements. Dobereiner termed a set of three elements a triad. Thus, chlorine, bromine, and iodine form a triad Dobereiner proposed several other triads (lithium-sodium-potassium, calcium-strontium-barium). Dobereiner recognized that there was some sort of relationship between elements, but many elements did not fit in any triad group, and even those triads proposed displayed numerous inconsistencies. 

The isotope lithium-7 has a mass of 7-0160 atomic mass units, and the isotope lithium-6 has a mass of 6.0151 atomic mass units. Given the information that 92.58 percent of all lithium atoms found in nature... 

How many atoms are there in a 6.941-gram sample of lithium, Li (atomic mass 6.941 atomic mass units) ... 

Because this number of grams of lithium is numerically equal to the atomic mass, there are 6.02 x 1023 atoms in the sample, which is 1 mole of lithium atoms. 

We can estimate an amount of substance needed to produce a solution as a check on our calculations, (a) Using mass numbers 7 for lithium, 12 for carbon and 16 for oxygen, estimate the amount of lithium carbonate needed to produce 1 L of a 3 M Li2CC>3 solution, (b) Now, perform the calculation using the atomic masses as a comparison. 

The process referred to is He - jLi + The calculation of the mass change only requires the whole number atomic masses of the elements since, if we add two electrons to each side, we would have enough for a whole helium atom on the left and a whole lithium atom on the right. 

Alkali metals have high oxidation-reduction potentials and low atomic masses. Thus they are attractive candidates for anodes in secondary batteries. In this context, it was shown in a couple of investigations that lithium and sodium can be electrodeposited from tetrachloroaluminate-based ionic liquids. 

For example, lithium exists as two isotopes lithium-7 and lithium-6. As you can see in Figure 5.4, lithium-7 has a mass of 7.015 u and makes up 92.58% of lithium. Lithium-6 has a mass of 6.015 u and makes up the remaining 7.42%. To calculate the average atomic mass of lithium, multiply the mass of each isotope by its abundance. 

Looking at the periodic table confirms that the average atomic mass of lithium is 6.94 u. The upcoming Sample Problem gives another example of how to calculate average atomic mass. 

A further special area of propulsion systems is Chemical Thermal Propulsion (CTP). CTP is defined in contrast to STP (solar thermal propulsion) and NTP (nuclear thermal propulsion). In CTP, in a very exothermic chemical reaction in a closed system, heat but no pressure is generated since the products of the reaction are solid or liquid. The heat energy is then transferred to a liquid medium (the propellant) using a heat exchanger, which is responsible for the propulsion of for example, the torpedo. Suitable propellants are e.g. water (the torpedo can suck it in directly from its surroundsings) or H2 or He, due to their very low molecular or atomic masses. The basic principles of CTP can also be used in special heat generators. A good example for a chemical reaction which is suitable for CTP is the reaction of (non-toxic) SF6 (sulfur hexafluoride) with easily liquified lithium (m.p. 180 °C) ... 

Calculate the atomic mass of lithium from the following data ... 

Most of the elements in nature are found as a mixture of isotope atoms. Therefore, determining the atomic mass of these elements can be problematic. For example, the lithium atom has two isotopes Li and Li. So, which number will be the atomic mass of Li, 6 or 7 In fact, the atomic mass of Li is exactly 6.94 amu. 

When the idea of relative atomic mass was first put forward, some chemists started to wonder whether there was a connection between the RAM of an element and its properties. One of these chemists, Dobereiner, in 1829, noticed that there were groups of three elements (triads) which had very similar chemical properties and in which the RAM of the middle element was almost exactly the average of the other two elements in the triad (these groups became knovm as Dobereiner s Triads). One triad was the three elements lithium, sodium and potassium all are soft metals, are highly reactive and have to be stored under oil. Their RAMs are lithium 7, sodium 23, potassium 39. As you can see, sodium s RAM is the average of 7 and 39. 

Calculate the nuclear binding energy of one lithium-6 atom. The measured atomic mass of lithium-6 is 6.015 amu. 

A revolutionary event in the primary battery market was the development of primary lithium batteries in 1973. Lithium is a very attractive metal for battery applications due to its low atomic mass (6.94), its high specific capacity (3.86 Ah g 1), and its high electrochemical reduction potential (—3.035 V) [10]. Research in lithium batteries started in the late 1950s. It was then... 

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