Identifying the Elements

Apparatus for the study of the volatile halides of elements 104 and 105 (reproduced with permission from J.V. Kratz, J. Alloys Compd., 1994, 213-214, 22). 

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Gr. thallos, a green shoot or twig) Thallium was discovered spectroscopically in 1861 by Crookes. The element was named after the beautiful green spectral line, which identified the element. The metal was isolated both by Crookes and Lamy in 1862 about the same time. 

When an argon plasma torch is used to identify the elements present in a sample or to measure isotope ratios, the sample must be introduced into the center of the plasma flame through an inlet tube. 

In X-Ray Fluorescence (XRF), an X-ray beam is used to irradiate a specimen, and the emitted fluorescent X rays are analyzed with a crystal spectrometer and scintillation or proportional counter. The fluorescent radiation normally is diffracted by a crystal at different angles to separate the X-ray wavelengths and therefore to identify the elements concentrations are determined from the peak intensities. For thin films XRF intensity-composition-thickness equations derived from first principles are used for the precision determination of composition and thickness. This can be done also for each individual layer of multiple-layer films. 

Auger electron spectroscopy (AES) is a technique used to identify the elemental composition, and in many cases, the chemical bonding of the atoms in the surface region of solid samples. It can be combined with ion-beam sputtering to remove material from the surface and to continue to monitor the composition and chemistry of the remaining surface as this surface moves into the sample. It uses an electron beam as a probe of the sample surface and its output is the energy distribution of the secondary electrons released by the probe beam from the sample, although only the Ai er electron component of the secondaries is used in the analysis. 

By visual inspection of an OAET it is possible to identify the elements of a process control task which are critical in responding to an initiating event. An important issue in the construction of OAETs is the level of task breakdown. If the overall task is redescribed to very small subtasks it might be difficult to gain insights from the OAET because it Ccin become relatively unwieldy. Hierarchical Task Analysis provides a useful framework for the... 

Strategy First identify the elements. Then (using Table 2.2 as necessary) identify the charges of the cation and anion. Finally, balance positive and negative charges. 

The following properties are observed for an unknown element. Identify the element from its properties, (a) The neutral atom has two unpaired electrons, (b) One of the valence electrons in the ground state atom has mt = 4 I. (c) The most common oxidation state is +4. (d) If an electron in a hydrogen atom were excited to the same principal quantum level, n, as the valence electrons in an atom of this element, and fell to the n — 1 quantum level, the photon emitted would have an energy of 4.9 X 10—20 J. 

The following Lewis structure was drawn for a Period 3 element. Identify the element. 

The high-temperature contribution of vibrational modes to the molar heat capacity of a solid at constant volume is R for each mode of vibrational motion. Hence, for an atomic solid, the molar heat capacity at constant volume is approximately 3/. (a) The specific heat capacity of a certain atomic solid is 0.392 J-K 1 -g. The chloride of this element (XC12) is 52.7% chlorine by mass. Identify the element, (b) This element crystallizes in a face-centered cubic unit cell and its atomic radius is 128 pm. What is the density of this atomic solid ... 

Self-Test 14.2A An element ( E ) in Period 4 forms a molecular hydride with the formula HE. Identify the element. 

Identify the element with the larger atomic radius in each of the following pairs (a) vanadium and titanium (b) silver and gold (c) vanadium and tantalum (d) rhodium and iridium. 

C03-0140. An element E forms a compound whose formula is ECI5. Elemental analysis shows that the compound is 85.13% by mass chlorine. Identify the element E. 

Balance the equation, (b) Identify the elements that change oxidation state, (c) Explain the metathesis portion of the reaction using hard-soft acid-base arguments. 

Charge number and mass number must be conserved in each reaction. Thus, each a particle decreases the nuclear charge by two units and the mass number by four units. Similarly, each P emission increases the nuclear charge by one unit but leaves the mass number unchanged. Consult a periodic table to identify the elemental S3Tnbol of each product nuclide. 

Spectroscopy continues to play important roles in chemistry, physics, and astronomy. Easy-to-use spectrometers enable chemists to rapidly identify the elements. Common organic molecules also have characteristic emission and absorption lines, making spectroscopy an invaluable tool for analyzing complex chemicals. 

Identify the element(s) oxidized and the element(s) reduced. Write a separate half-reaction for each of these. 

Identifying stars in globular and open clusters as either old stars from the primordial explosion or new stars formed after a supernova event is based on the atomic composition of the stars. The primary way of identifying the elements in any excited state is to study the atomic spectroscopy of the stellar spectrum, such as in Figure 4.2 and identify the atoms by assigning the spectra. This becomes a complicated process for the heavier elements but is very informative even for the simple H-atom spectra. 

Determine the atomic weight of the unknown element for each case, identify the element and compound.. 

Using the intensities of the isotope peaks try to identify the elemental composition of all the ions (where it is possible). Calculate the unsaturation degree of these ions. 

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