Chemistry Library

<?php
    /*
    PHP Chemistry Library
    
    Copyright (c) 2009, reusablecode.blogspot.com; some rights reserved.
    
    This work is licensed under the Creative Commons Attribution License. To view
    a copy of this license, visit http://creativecommons.org/licenses/by/3.0/ or
    send a letter to Creative Commons, 559 Nathan Abbott Way, Stanford, California
    94305, USA.
    */
 
    // Elements by name
    $elementNames = array(null, 
        "Hydrogen", "Helium", "Lithium", "Beryllium", "Boron", "Carbon", "Nitrogen", "Oxygen", "Fluorine", "Neon",
        "Sodium", "Magnesium", "Aluminium", "Silicon", "Phosphorus", "Sulfur", "Chlorine", "Argon", "Potassium", "Calcium",
        "Scandium", "Titanium", "Vanadium", "Chromium", "Manganese", "Iron", "Cobalt", "Nickel", "Copper", "Zinc",
        "Gallium", "Germanium", "Arsenic", "Selenium", "Bromine", "Krypton", "Rubidium", "Strontium", "Yttrium", "Zirconium",
        "Niobium", "Molybdenum", "Technetium", "Ruthenium", "Rhodium", "Palladium", "Silver", "Cadmium", "Indium", "Tin",
        "Antimony", "Tellurium", "Iodine", "Xenon", "Caesium", "Barium", "Lanthanum", "Cerium", "Praseodymium", "Neodymium",
        "Promethium", "Samarium", "Europium", "Gadolinium", "Terbium", "Dysprosium", "Holmium", "Erbium", "Thulium", "Ytterbium",
        "Lutetium", "Hafnium", "Tantalum", "Tungsten", "Rhenium", "Osmium", "Iridium", "Platinum", "Gold", "Mercury",
        "Thallium", "Lead", "Bismuth", "Polonium", "Astatine", "Radon", "Francium", "Radium", "Actinium", "Thorium",
        "Protactinium", "Uranium", "Neptunium", "Plutonium", "Americium", "Curium", "Berkelium", "Californium", "Einsteinium", "Fermium",
        "Mendelevium", "Nobelium", "Lawrencium", "Rutherfordium", "Dubnium", "Seaborgium", "Bohrium", "Hassium", "Meitnerium", "Darmstadtium",
        "Roentgenium"
    );
 
    // Elements by symbol
    $elementSymbols = array(null,
        "H", "He", "Li", "Be", "B", "C", "N", "O", "F", "Ne",
        "Na", "Mg", "Al", "Si", "P", "S", "Cl", "Ar", "K", "Ca",
        "Sc", "Ti", "V", "Cr", "Mn", "Fe", "Co", "Ni", "Cu", "Zn",
        "Ga", "Ge", "As", "Se", "Br", "Kr", "Rb", "Sr", "Y", "Zr", 
        "Nb", "Mo", "Tc", "Ru", "Rh", "Pd", "Ag", "Cd", "In", "Sn",
        "Sb", "Te", "I", "Xe", "Cs", "Ba", "La", "Ce", "Pr", "Nd",
        "Pm", "Sm", "Eu", "Gd", "Tb", "Dy", "Ho", "Er", "Tm", "Yb",
        "Lu", "Hf", "Ta", "W", "Re", "Os", "Ir", "Pt", "Au", "Hg", 
        "Tl", "Pb", "Bi", "Po", "At", "Rn", "Fr", "Ra", "Ac", "Th",
        "Pa", "U", "Np", "Pu", "Am", "Cm", "Bk", "Cf", "Es", "Fm",
        "Md", "No", "Lr", "Rf", "Db", "Sg", "Bh", "Hs", "Mt", "Ds",
        "Rg"
    );
 
    // List of subshell names in order of filling.
    $subshells = array("1s", "2s", "2p", "3s", "3p", "4s", "3d", "4p", "5s", "4d", "5p", "6s", "4f", "5d", "6p", "7s", "5f", "6d", "7p", "8s", "5g", "6f", "7d", "8p", "9s", "6g", "7f", "8d", "9p", "10s", "6h", "7g", "8f", "9d", "10p", "11s", "7h", "8g", "9f", "10d", "11p", "12s", "7i", "8h", "9g", "10f", "11d", "12p", "13s", "8i", "9h", "10g", "11f", "12d", "13p", "14s");
 
    // Retrieve element name, with support for elements that don't have names yet.
    // REQUIRES: strtoproper()
    function getElementName($atomicNumber)
    {
        $result = "";
        $roots = array("nil", "un", "bi", "tri", "quad", "pent", "hex", "sept", "oct", "enn");
 
        if ($atomicNumber <= count($elementNames) - 1)
        {
            $result = $elementNames[$atomicNumber];
        }
        else
        {
            for ($i = 1; $i <= strlen($atomicNumber); $i++)
            {
                $result .= $roots[substr($atomicNumber, $i, 1)];
            }
 
            $result = strtoproper(result) . "ium";
 
            // If bi or tri is followed by the ending ium (i.e. the last digit is 2 or 3), the result is '-bium' or -'trium', not '-biium' or '-triium'.
            $result = str_replace("ii", "i", $result);
 
            // If enn is followed by nil (i.e. the sequence -90- occurs), the result is '-ennil-', not '-ennnil-'.
            $result = str_replace("nnn", "nn", $result);
        }
 
        return $result;
    }
 
    // Retrieve element symbol, with support for elements that don't have symbols yet.
    // REQUIRES: strtoproper()
    function getElementSymbol($atomicNumber)
    {
        $result = "";
        $symbols = array("n", "u", "b", "t", "q", "p", "h", "s", "o", "e");
 
        if ($atomicNumber <= count($elementSymbols) - 1)
        {
            $result = $elementSymbols[$atomicNumber];
        }
        else
        {
            for ($i = 1; $i <= strlen($atomicNumber); $i++)
            {
                $result .= $symbols[substr($atomicNumber, $i, 1)];
            }
 
            $result = strtoproper($result);
        }
 
        return $result;
    }
 
    // Returns the maximum number of electrons allowed in the specified subshell.
    function maxElectrons($subshell)
    {
        switch (strtolower(substr($subshell, -1)))
        {
            case "s":
                return 2;
                break;
            case "p":
                return 6;
                break;
            case "d":
                return 10;
                break;
            case "f":
                return 14;
                break;
            case "g":
                return 18;
                break;
            case "h":
                return 23;
                break;
            case "i":
                return 26;
                break;
        }
    }
 
    // Calculate the electron configuration for a given atom.
    function electronConfiguration($atomicNumber)
    {
        $electrons = $atomicNumber;
        $configuration = "";
 
        foreach ($subshells as $subshell)
        {
            if ($electrons > $maxElectrons($subshell))
            {
                // A d subshell that is half-filled or full (ie 5 or 10 electrons) is more stable than the s subshell of the next shell.
                if ($subshell == "4s" && ($atomicNumber == 24 or $atomicNumber == 29)) || ($subshell == "5s" && ($atomicNumber == 41 || $atomicNumber == 42 || $atomicNumber == 44 || $atomicNumber == 45 || $atomicNumber == 47)) || ($subshell == "6s" && ($atomicNumber == 78 || $atomicNumber == 79))
                {
                    $configuration .= " $subshell^1";
                    $electrons--;
                }
                // Special exception for palladium.
                elseif ($subshell == "5s" && $atomicNumber == 46)
                {
                    // do nothing; this subshell gets no electrons
                }
                else
                {
                    $configuration .= " $subshell^" . $maxElectrons($subshell);
                    $electrons -= $maxElectrons($subshell);
                }
            }
            else
            {
                $configuration .= " $subshell^$electrons";
                $electrons = 0;
                break;
            }
        }
 
        return trim($configuration);
    }
?>