Lowest letters

Lowest letters (lowest means a lower than b, etc.) in the expression of ring junctions in fusion nomenclature. 

Generally, many isomers are possible for fused systems and these have to be differentiated by appropriate descriptors. To obtain these, the sides of the parent component are labelled consecutively by italic letters a, b, c... tracing the locant path 1,2,3,4. .. and ignoring potential non-standard numbering. For the attached secondary components the inherent numbering is maintained. Combination of the partial names is then effected by intercalating the fusion locants in square brackets between the component names. Clearly, the principle of lowest locants is to be respected here too first, lowest letters for the base component second, lowest numbers for the higher order components the sequence of numbers follows... 

If the same alkyl group occurs more than once as a side chain, this is indicated by the prefixes di-, tri-, tetra-, etc. Side chains are cited in alphabetical order (before insertion of any multiplying prefix). The name of a complex radical (side chain) is considered to begin with the first letter of its complete name. Where names of complex radicals are composed of identical words, priority for citation is given to that radical which contains the lowest-numbered locant at the first cited point of difference in the radical. If two or more side chains are in equivalent positions, the one to be assigned the lowest-numbered locant is that cited first in the name. The complete expression for the side chain may be enclosed in parentheses for clarity or the carbon atoms in side chains may be indicated by primed locants. 

The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) may be identified by finding the point where the occupied/virtual code letter in the symmetry designation changes from O to V. 

J. M. (1998) Lowest Energy Structures of Gold Nanoclusters. Physical Review Letters, 81, 1600-1603. 

In the lowest energy state (called the ground state) of Al, the electrons occupy various quantum states written Is2 2s2 2p6 3s2 3p Here the precursor numbers (called the principal quantum numbers) give the total energy of the state the letters describe the nature of the state and the superscripts give the number of electrons in each state (the sum of the superscripts = 13). The energy levels of the electrons in Al are ... 

The lowest energy state is that characterized by n = 1, which requires that 1 = 0 and m = 0. A state for which 1 = 0 is designated as an s state so the lowest energy state is known as the Is state, since states are designated by the value of n followed by a lower case letter to represent the 1 value. The values of 1... 

In the International Tables of Crystallography, for each of the 230 space groups the list of all the Wyckoff positions is reported. For each of the positions (the general and the special ones) the coordinate triplets of the equivalent points are also given. The different positions are coded by means of the Wyckoff letter, a, b, c, etc., starting with a for the position with the lowest multiplicity and continuing in alphabetical order up to the general position. 

The ordered listing of the chemical compounds in Table A2 is the same as that in the JANAF tables and is alphabetical according to the chemical formula with the lowest order letter in the formula determining the position. The thermochemical tables have the following order ... 

Figure 2. Potential energy diagram for nitrosamide photoreaction. The letters with asterisks represent the lowest singlet excited states.

Table 2. Energies (in kcal/mol) of the 10 lowest energy decoys of the final population with backbone RMS deviation to the NMR structure and secondary structure content. The first row designates the secondary structure content of the NMR structure.. The letters H and c indicate amino acids in Helix and coil structure respectively. Green letters indicate correct, red incorrect secondary structure.

Each orbital can therefore contain no more than two electrons, with opposite spin quantum numbers. This rule, which affects the order in which electrons may fill orbitals, is known as the Pauli exclusion principle. Table 2.3 summarizes the configuration of electron orbitals for the first three shells. The orbitals are labeled with the numerical value of n and a letter corresponding to the value of l (s, p, d, f..). As you can see from Table 2.3, the n = 1 shell can hold up to two electrons, both in the s orbital, the n - 2 shell can hold up to eight electrons (2 in the s and 6 in the p orbital), the n - 3 can hold up to 18 electrons (2 s, 6 p, and 10 d), and the n 4 shell can hold up to 32 electrons (2 s, 6 p, 10 d, and 14 f). The lowest energy orbitals are occupied first. So for hydrogen, which has one electron, the electron resides in the Is orbital. For lithium, which has three electrons, two are in the Is orbital and the third is in the 2s orbital. For silicon (Z = 14), there are two electrons in Is, two electrons in 2s, six electrons in 2p, two electrons in 3s, and two electrons in 3p. 

The series of ions related by similar structure or common origin will be denoted as capital letters (A, B, C,. .. Y, Z, AA, BB, CC,. ..). The subscript numeral will denote the number of steps needed for the formation of the fragment from the molecular ion, and the superscript numeral, the ordinal number of the isomeric ion. The lowest ordinal number is given to the isomer having the substituent at the carbon atom of lowest ordinal number or, respectively, containing the lowest ordinal carbon atoms.13 For example, the symbol A means that the ion arises as the result of a two-step transformation of M ion, being the second of several possible isomers. 

The possible stationary energy levels of electrons are named either by letters, K, L, M, N, O. .. or by positive integer numbers starting from the lowest energy level. These numbers are generally denoted by n where n = 1, 2, 3,. .. 

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