ATOMIC NUMBER Z

Tabulated buildup factors depend on the type of primary radiation, the energy, E, of the primary radiation, the charge, Z, atomic number, A, and thickness of the shielding material. 

Where Z = atomic number, A — atomic weight, E the electron energy (keV), and p the density (g/cm3). 

The efficient screening approximation means essentially that the final state of the core, containing a hole, is a completely relaxed state relative to its immediate surround-ing In the neighbourhood of the photoemission site, the conduction electron density of charge redistributes in such a way to suit the introduction of a core in which (differently from the normal ion cores of the metal) there is one hole in a deep bound state, and one valence electron more. The effect of a deep core hole (relative to the outer electrons), may be easily described as the addition of a positive nuclear charge (as, e.g. in P-radioactive decay). Therefore, the excited core can be described as an impurity in the metal. If the normal ion core has Z nuclear charges (Z atomic number) and v outer electrons (v metallic valence) the excited core is similar to an impurity having atomic number (Z + 1) and metalhc valence (v + 1) (e.g., for La ion core in lanthanum metal, the excited core is similar to a Ce impurity). 

The number of nucleons is equal to the sum of the number of protons (Z = atomic number) and number of neutrons (N) in the nucleus and is defined as the mass number (A = nucleon number)... 

Atomic Number (Z) Atomic Number of an element is equal to the number of protons in its nucleus. In a neutral atom the number of protons is the same as the number of electrons. 

A frustrating feature of x-ray fluorescence measurement is the radiationless energy transfer from higher Z (atomic number) elements to lower Z contiguous elements or multiple scattering, making the former appear to be at a lower concentration and the latter to be at a higher concentration than they actually are. Compensation for these factors will receive careful study to avoid serious analysis error. 

Mass spectrometry is based on the physical properties of the atomic nucleus. The atomic nucleus of any chemical element consists of protons and neutrons. In an electrically neutral atom the number of positively charged protons in the nucleus equals the number of negatively charged electrons in the shells. The number of protons (Z = atomic number) determines the chemical properties and the place of the element in the periodic table of the elements. The atomic number Z of a chemical element is given as a subscript preceding the elemental symbol (e.g., jH, gC, 17CI, 2eF or 92 )-Besides the protons, uncharged neutrons with nearly the same mass in comparison to the protons (m = 1.67493 x 10 kg versus nip = 1.67262 x 10 kg) stabilize the positive atomic nucleus. In contrast to the mass of the protons and neutrons in the nucleus, the mass of the electrons is relatively small at = 9.10939 x 10 kg. 

Table 2 Bound scattering lengths, i>(fm) and cross section for selected isotopes and for selected naturally occurring isotopic mixtures of the elements u(hams, 1 bam = 100 fm ). Z, atomic number A, mass number I, spin of the nuclear groimd state i>coh> bine, coherent and incoherent scattering lengths ffa, ffeCh, coherent and incoherent cross sections ffa, absorption cross section for 2.2 km s neutrons ...

Where published values of F2, F4, Fq, and were not available, initial assignments were based on levels calculated from the parameters F and f which were obtained by extrapolation from neighboring members of the series (4). Both F2 and can be assumed to be approximately linear functions of Z (atomic number) within the series, and by using the ratios F4/F2 and Fq/F2 calculated for a 4/ or 5f hydrogenic eigenfunction (15), all three electrostatic parameters can be evaluated from F2 alone. 

The values of F2 for the trivalent lanthanides and actinides are plotted vs. Z (atomic number) in Figure 7, and those of f are shown graphically in Figure 8. Values of F2 and 5/ for actinides above curium were extrapolated from the light half of the series assuming a linear relationship for the parameters (9). These parameters, in turn, were used to calculate the expected energy levels for Es ", and Fm-" ". ... 

This is significantly lower value than for either Rb or Ag. First the difference for H atom only the energy of an electron in a hydrogenic atom is inversely proportional to the square of the principal quantum number n. Hence we can expect a sharp decrease in 7 with an increase in n (i.e. from l3.6eV for n = 1 to 0.544eV for n = 6). The difference between H(5s ) on one side and Rb and Ag on the other lies in Z (atomic number or nuclear charge or... 

Z, atomic number L, principal quantum number Z , number of valence electrons , van der Waals atomic radius covalent radius m, atomic mass , van der Waals volume Sanderson electronegativity a, atomic polarizability (10 " cm ) IP, ionization potential (eV) EA, electron affinity (eV). 

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