Lowercase atomic symbol

Atom symbols are written normally the first letter should be capitalized (usage of lowercase symbols is discussed below). 

To simplify encoding of aromatic compounds, special notation was devised. When atom symbols are written in lowercase letters, aromatic bonds are implied between atoms (unless a different bond is explicitly given). For example, benzene can be written as clcccccl, whereas while C1CCCCC1 means cyclohexane. 

Aromatic bonds are given explicitly using a colon ( ) it is not possible to use a lowercase letter for an atom symbol for specification of aromatic bonds. 

An asterisk C) stands for any nonhydrogen atom, — for a single bond, = for a double bond, for a triple bond, for an aromatic bond atomic symbol in lowercase means that the atom is part of an aromatic system. 

It is convenient to use symbols for the atoms of the different elements. An atomic symbol is a one- or two-letter notation used to represent an atom corresponding to a particular element. Typically, the atomic symbol consists of the first letter, capitalized, from the name of the element, sometimes with an additional letter from the name in lowercase. For example, chlorine has the symbol Cl. Other symbols are derived from a name in another language (usually Latin). Sodium is given the symbol Na from its Latin name, natrium. Sjunbols of selected elements are fisted in Table 2.1. 

Symbol one- or two-letter representation of an element or an atom of an element. The first letter of a symbol is capitalized the second letter, if any, is lowercase. 

Figure 2.1 The contiriuum in bonding from covalent to ionic is a result of an unequal distribution ot bonoing electrons between atoms. The symbol 8 (lowercase Greek delta means part/a/charge, either partial positive ((S+) for the electron-poor atom or partial negative (o-) fnr the electron-rich atom.

Benzene is typically thought of as a combination of two equivalent resonance structures. These could be written as the SMILES C1=C-C=C-C=C1 and C1-C=C-C=C-C=1. In order to have just one representation for benzene and other aromatic systems, SMILES handles these aromatic systems specially, treating the atoms in an aromatic ring as a special aromatic type and the bonds as a special aromatic type. The lowercase symbol is used to denote an aromatic atom in SMILES and SMARTS. The SMILES for benzene then becomes clcccccl. A bond between aromatic atoms is an aromatic bond, unless otherwise spelled out. For example, biphenyl can be written as clcccccl-clcccccl. 

Solving Schrodinger s equation for the hydrogen atom leads to a series of mathematical functions called wave functions that describe the electron in an atom. These wave functions are usually represented by the symbol ip (lowercase Greek letter psi). Although the wave function has no direct physical meaning, the square of the wave function, provides information about the electron s location when it is in an allowed energy state. 

An elemental symbol is based on the element s name and consists of a single capital letter or a capital letter followed by a lowercase letter. The symbols for 11 elements are based on the element s name in Latin or German. An elemental symbol is sometimes used to represent an element in a general way or to represent a single atom of an element. I Table 2.1 hsts the elements whose names and symbols have been agreed on. 

Symbols based on names have been assigned to every element. Most consist of a single capital letter followed by a lowercase letter. A few consist of a single capital letter. Compounds are represented by formulas made up of elemental symbols. The number of atoms of each element in a molecule is shown by subscripts. 

Much of what we have seen for one-electron ions continues to hold for many-electron atoms or ions. All the symbolism is the same, except that capital letters replace lowercase The quantum numbers are L, S, and J, and the main symbol becomes S, P, D, F, G, etc. There is a total orbital angular momentum vector L with quantum number L that equals the maximum value of Mi. The length of L is a.u., and it... 

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