Abstract:
A chemical calculator providing rapid and convenient ways to retrieve information and perform calculations of chemical elements and chemical formulas obtained by direct entry from a periodic table keypad. Chemical element data, such as atomic number and mass, or calculated data (e.g. bond distance) of element pairs are displayed on an LCD or CRT screen when element keys are selected. Chemical formulas can be written when element, numerical or formulaic keys are pressed. The &#34;Enter&#34; command results in the display of the chemical formula&#39;s condensed formula, formula weight and percentage composition. Other function modes permit additional transformations, reaction yields and limiting reactants and empirical formula determinations.

Description:
FIELD OF THE INVENTION 
     The present invention relates to computers for locating information about chemical elements and using that information to make calculations, derive formulae, and display same. 
     BACKGROUND OF THE INVENTION 
     The location of information about chemical elements and the use of that information for calculations or other purposes is a time-consuming as well as error prone process. Persons interested in working on complex chemical problems or calculations that are based on chemical element information are hindered by the time and convenience of locating the necessary information. Although there are available computer programs or calculators that assist in the retrieval and processing of this information, none are available in a convenient and portable form (such as found in a scientific calculator). 
     The following describes the types of problems that a chemical calculator could solve for the beginning chemistry student to a professional chemist, chemical engineer or other persons having a need to solve these kinds of chemical problems. The questions below are those that are typically found in chemistry textbooks or chemistry reference works. The steps required to answer these questions are followed by a brief notation as to the types of difficulties likely to be encountered or sources of error. 
     Question #1: What is the name, atomic number and mass, electron configuration and melting point of the element having the symbol &#34;A1&#34;? 
     Answer: Aluminum, at.no.=13, at.mass=26.9815, e.configuration.=[Na]3s 2  3p 1 , m.pt.=660° C. 
     Steps Involved in Answering This Question: Typically a person would check a periodic table or reference table (found in a reference handbook, separate attachment or wall chart). Any of these reference sources may not be readily available if the person is in a laboratory or plant, classroom or in the field. In addition, the reference source may not have all of the information, e.g. many condensed periodic tables may have only information about the first three. Even a large wall chart may not be readable to more than a few entries to a person at the back of a classroom. 
     Question #2: What is the difference in electronegativity and % ionic character in the bond between sodium and chlorine? 
     Answer: E.N. diff.=3.0-1.0=2.0, % ionic character=63% 
     Steps Involved in Answering This Question: Along with the problems of locating a source containing the electronegativity values (as described for Question #1 above), there is also the problem of knowing how to calculate the % ionic character. 
     Question #3: What is the constituent formula and formula weight of Al 2  (SO 4 ) 3  +2.5 H 2  O? 
     Answer: Formula=Al 2  S 3  O 14 .5, F.W.=387.18575 
     Step 1: Write the formula 
     Step 2: Locate atomic mass of constituent elements 
     Step 3: Set up for calculations 
     
         ______________________________________3.1 2     Al    =   2   ×                       26.9813                              =   53.9626                                         =    53.96263.2 1     S     =   1   ×                       32.064 =   32.0643.3 4     O     =   4   ×                       15.9994                              =   63.99763.4 3 (SO.sub.4) = 3 ×                    96.0616  =   288.18483.5                                   343.14743.6 2     H     =   2   ×                       1.00797                              =    2.015943.7 1     O     =   1   ×                       15.9994                              =   15.99943.8 2.5 (H.sub.2 O) = 2.5 ×                    18.01534 =    45.038353.9 Formula Weight            =     387.18575______________________________________ 
    
     Sources of Errors and Difficulties: There are some dozen separate steps or operations that must be performed to answer the question. Examples of the major types of errors are: 
     Steps 1-3: Incorrect formula entry and set-up so that subscripts and/or coefficients multiply proper quantities. In steps 3.3 and 3.4, for example, the atomic mass of oxygen must be multiplied (step 2.3) by 4 before the sum within the parentheses is multiplied by 3 (step 3.4). 
     Step 2: Involves the location and transcription of the correct atomic weight of the element (beginning students often use the atomic number instead of the atomic mass). 
     Step 3: The use of computers or math calculators does speed up the actual calculation process, but a common source of error arises from typographical errors in number entry. (For example, this author obtained two slightly different answers to the question the two times they were tried due to minor typographical errors.) 
     Step 3.8: The student must recognize the significance and operation of the coefficient &#34;2.5&#34; that is multiplied times the formula weight of H 2  O and this added to the formula weight of the first part of the formula. 
     Question 4: What is the % (by weight) of the constituent elements found in the formula given in Question #3? 
     
         ______________________________________Answer:     13.937% Al       24.843% S   88.324% Al.sub.2 (SO.sub.4).sub.3       49.587% Oplus        1.360% H                   11.683% H.sub.2 O       10.331% O______________________________________ 
    
     Description of Process for Solution: The first steps in the calculations are similar to that used for Question #3, except that it is necessary to separate the weights constituted by each element from the remainder of the formula: 
     
         ______________________________________In the First Part of the Formula:4.01: for Al, there are 2 Al = 2 × 26.9626 =       53.96264.02: for S, there are 3 S (1 S in each SO.sub.4) = 3 × 32.064 =        96.1924.03: for O, there are 12 O (4 O in each SO.sub.4) = 12 × 15.9994 =     191.9928In the Second Part of the Formula:4.04: for H, there are 5 H (2 H in H.sub.2 O) = 2 × 2.5 × 1.00797 =                           5.264854.05: for O, there are 2.5 O (1 O in H.sub.2 O) = 2.5 × 15.9994 =     39.9985 Formula Weight =         387.4108______________________________________ 
    
     The % composition for each element is obtained by dividing the weights obtained in Steps 4.01-4.05 by the formula weight: 
     
         4.06: ( 53.9626/387.4108)×100=13.929% Al 
    
     
         4.07: ( 96.192/387.4108)×100=24.829% S 
    
     
         4.08: (191.9928/387.4108)×100=49.558% O 
    
     
         4.09: ( 5.26485/387.4108)×100=1.359% H 
    
     
         4.10: ( 39.9985/387.4108)×100=10.324 % O 
    
     Question #5: What is the a) (constituent) element formula and b) empirical formula corresponding to the following? 
     
         CH.sub.3 (CH.sub.2).sub.3 COCCl.sub.2 CO.sub.2 CH.sub.2 OH 
    
     Answer: 
     Constituent element formula: C 8  H 12  O 4  Cl 2   
     Empirical formula: C 4  H 6  O 2  Cl 
     Description of Process for Solution: To answer 5a), the procedure is relatively straight-forward, i.e. you simply count the number of atoms of each element: CH 3  (CH 2 ) 3  COCCl 2  CO 2  CH 2  OH 
     
         __________________________________________________________________________Counting:  CH.sub.3 --(CH.sub.2).sub.3 --C--O--C--Cl.sub.2 --C--O.sub.2  --CH.sub.2 --O--H          Total__________________________________________________________________________for C: 131--1--1--1----            8 Cfor H: 36------------2--1         12 Hfor O: ------1------2--1--         4 Ofor Cl:  ----------2----------       2 ClFormula = C.sub.8 H.sub.12 O.sub.4 Cl.sub.2__________________________________________________________________________ 
    
     Although this counting would appear to be rather straight-forward, the miscounting of only one element or summing error would produce a completely erroneous result. 
     To obtain an empirical formula, the constituent element formula obtained above must be examined to see if all of the subscripts are divisible by any number to produce the &#34;simplest&#34; empirical formula, i.e. that represent the formula that shows a ratio of the fewest atoms of the constituent elements that would be obtained by %-composition analysis (see Question #8 below). In this case, the subscripts are all divisible by 2 to give: C 4  H 6  O 2  Cl. 
     Question #6: What is the formula weight, constituent formula and % composition of the reactant A and product B shown in the following transformation? 
     
         ______________________________________ ##STR1## ##STR2## ##STR3##______________________________________ ##STR4##______________________________________ 
    
     Solution to Question #6: 
     1. The constituent formula of reactant A is calculated following the procedures illustrated for the solution to Questions #4 and #5. The formula weight and % composition are then calculated using this formula as shown in the solution to Question #4. 
     2. Typically, the person trying to determine the constituent formula and/or formula weight of product B would recognize that formula B is related to formula A by the &#34;loss&#34; of H 2  O and &#34;gain&#34; of CH 3  C 2  OH[C 2  H 6  O] in the transformation and would set up the calculation as follows: ##STR5## The formula weight of B can then be determined by either subtracting and adding (respectively) the formula weights of H 2  O (18.0152) and C 2  H 6  O (46.0688) from the formula weight of A: ##STR6## or by using the formula of B to calculate its formula weight: ##EQU1## 
     While either of these procedures yield the same result, only the latter is useful in calculating the % composition: ##EQU2## 
     Suffice it to say, a number of steps must be taken and the choice of steps depends on the type of information or result desired. (The writer of this example spend in excess of 20 minutes setting up the mathematical operations to solve these questions. While the use of a calculator speeds up the process, it is not uncommon to still have a result that contains a mathematical error.) 
     Question #7: How many grams of product B (Question #6) would be obtained from 5.16 g of A? 
     Answer: 6.41 g of B 
     Solution to Question #7: Typically, the solution to this problem is obtained by determining the number of moles of A corresponding to 5.16 g. ##EQU3## According to the transformation, 0.04442 moles of B should be formed, therefore: ##EQU4## 
     As before, two separate mathematical operations must be performed in order to answer this question. Additional calculations would be required if the coefficients of the reactants and products in the chemical reaction shown in Question #6 were not all the same. 
     Question #8: What is the empirical formula of the substance whose composition is: 
     % C=28.22 
     % H=5.92 
     % O=28.19 
     % S=37.66 
     Answer: C 4  H 10  O 3  S 4   
     Description of Process: The first step in answering this question involves dividing the % values for each element by the atomic weight of that element. This gives a formula in which the subscripts of the formula are proportional to the ratios of the atoms of the constituent elements in the compound: 
     
         8.01 for C=28.22/12.01115=2.34948 
    
     
         8.02 for H=5.92/1.00797=5.87319 
    
     
         8.03 for O=28.19/15.9994=1.76194 
    
     
         8.04 for S=37.66/32.064=1.17452 
    
     First-decision Empirical Formula: 
     
         C.sub.2.34948 H.sub.5.87639 O.sub.1.76194 S.sub.1.117452 
    
     At this point, the goal is to reduce the formula to obtain whole number subscripts (i.e. you can not have &#34;fractions&#34; of atoms). While in come cases it might be possible to &#34;round off&#34; the numbers, typically this is not done at this point. Rather, the numbers are divided by the lowest value; in this case, 1.17452, for sulfur. 
     
         8.05 for C=2.34948/1.17452=2.00037 
    
     
         8.06 for H=5.87369/1.17452=5.00050 
    
     
         8.07 for O=1.76194/1.17452=1.50014 
    
     
         8.08 for S=1.17452/1.17452=1.00000 
    
     The new formula, rounding off to 2 decimal places is now: 
     
         C.sub.2.00 H.sub.5.00 O.sub.1.50 S.sub.1.00 
    
     At this point, it seems obvious that to obtain simple whole-number ratios of atoms, the formula subscripts should be multiplied by 2 to give the empirical formula: 
     
         C.sub.4 H.sub.10 O.sub.2 S.sub.2 
    
     Suffice it to say, this process involves several points of decision as to division or multiplication operations or rounding-off. The repetition of these decisions and mathematical operations account for significant introduction of transmission errors. 
     Question #9: What amount of product D is formed from 3.16 g of reactant C in the following chemical reaction? ##EQU5## Answer: 3.32 g (0.0313 moles) of D 
     Description of Process: The first step involves determining the number of moles of reactant C: ##EQU6## The formula weight of C must be determined as before. The second step involves setting up a ratio of moles C used to moles D produced according to the chemical equation: ##EQU7## 
     Again, the set-up required to answer this question is time-consuming and error-prone. Typically, the answer will be in error by some ratio of the coefficients of the reactants and products involved in the calculation. 
     The Prior Art 
     Dubois et al, U.S. Pat. No. 4,085,443, disclose a computer having a keyboard for encoding and inputting thereto alphabetic and graphic data relating to chemical compounds. 
     Ulyanov et al, U.S. Pat. No. 4,205,391 disclose a computer having an encoding tablet serving purposes similar to those of Dubois et al. 
     Cameron, U.S. Pat. No. 4,689,753 discloses a calculator for stoichiometric conversions. 
     Hewlett Packard HP48SX Scientific calculator has a display of a blank periodic table format. 
     SUMMARY OF THE INVENTION 
     The present invention (a chemical calculator) provides a rapid and convenient means to retrieve and calculate from information about chemical elements and chemical formulas by direct entry from a periodic table keyboard. The invention comprises a portable keyboard or key pad containing approximately 100 &#34;element&#34; keys arranged in a periodic table format (along with other standard calculator/PC keys) connected to a computer and an LCD (or CRT) display screen. The type of information retrieved depends on the function/mode selected by pressing the appropriate one of keys labeled F2 through F10, which have been labeled with self-explanatory mnemonics, as indicated parenthetically in the following description of the modes of operation of the calculator of my invention. In the description to follow, it is to be supposed that the first key pressed will be a function or mode key. Thereafter, key pressings will be treated in the mode just established until an ENTER key is pressed in order to process data in accordance with that mode and evoke the appropriate display. 
     In Mode 1 (&#34;ELEM&#34;,F2), when the user presses an element key, and then the ENTER key, the screen will display information about the element (e.g. the element name, atomic number and mass, electron configuration, melting/boiling point, etc.) drawn from the chemical element database. For example, the electron configuration for atomic fluorine would be displayed as 1s 2  2s 2  2p 6 . 
     In this mode, it is also possible to obtain the properties of groups or periods of chemical elements by pressing the Group/Period keys above or to the left of the vertical/horizontal rows, respectively, in the periodic table. 
     In Mode 2 (&#34;PAIR&#34;,F)), on pressing any two of the element keys, the display will provide calculated information derived from the chemical element database; such as interatomic bond lengths, electronegativity difference, % ionic character, etc. 
     In Mode 3 (&#34;FORM&#34;,F4), the user enters a chemical formula created by pressing 1) element keys, 2) subscript/coefficients, or 3) parentheses. Corrections or modifications of the displayed chemical formula can be done by moving through the formula with the cursor keys followed by element deletions and insertions. Then, pressing of the ENTER key displays; 
     A) the calculated formula weight corresponding to the chemical formula. 
     B) the % composition (of the constituent elements) 
     C) the chemical formula (of constituent elements). 
     For example, keying in Ca,3,(,P,O,4,),2,ENTER would evoke the display of Ca 3  (PO 4 ) 2 . Then ENTER again would display the formula weight as calculated by the computer. 
     In Mode 4 (&#34;CALC&#34;,F5) chemical formulas generated under this mode can be mathematically manipulated. Example: If a person wanted to know what the new formula weight of compound B produced from A (whose formula weight had previously been determined) in the transformation: ##EQU8## 
     Pressing the minus (-) key followed by keying in H,2,O; next pressing the addition (+) key, followed by keying in C,H,3,C,H,2,O,H; then pressing ENTER would display the condensed formula of B, C 8  H 16  O 2 , along with its formula weight and percentage composition. 
     In Mode 5 (&#34;RXN&#34;,F6) chemical reactants/products can be entered as formulas (as in Mode 3) and the chemical reaction can be balanced, and otherwise manipulated to determine yields, limiting reactants, etc. See Question #9, Background of the invention, supra. 
     In Mode 6 (&#34;EMP&#34;,F7), the empirical formula of a compound can be determined by entering the element and its % composition or measurement. Pressing ENTER then produces the calculated subscripts for the chemical formula, which can then be manipulated by division/multiplication for the purpose of obtaining whole-number subscripts. 
     The molecular formula can be obtained of the compound if the molecular formula weight is known. 
     In Other Modes (F8-F10) specialized information or calculated information derived from the database can be set up using a customized database. For example: 
     In Mode 7 (&#34;ISTP&#34;,F8), the properties (e.g. half-life, nuclear decay products, etc.) of an element&#39;s nucleides (isotopes) are obtained by pressing an element key. 
     In Mode 8 (M/E,F9), upon entering a chemical formula (as in Mode 3), the m/e peaks and relative intensity in a mass spectrum can be obtained. 
     In other modes, keying in standard chemical names would cause the corresponding formulae to be displayed. Conversely, keying in formulae would call up corresponding names. 
     The F1 key, labeled &#34;HELP&#34;, is considered Mode O, and has the usual type of &#34;HELP&#34; function by which the user can call up &#34;help&#34; messages which might assist him in using the machine, as by explaining the modes, etc. Since Mode O does not require entry of data by the user, preferably pressing F1 above will evoke the &#34;HELP&#34; messages. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a box diagram of a chemical calculator in accordance with the invention; 
     FIG. 2 is a plan view of one form that a chemical calculator in accordance with the invention may take in practice; 
     FIG. 3 illustrates an alternative to the FIG. 2 form of the invention; 
     FIG. 4 illustrates an alternate form of data entry device for use in the chemical calculator in accordance with the invention; 
     FIG. 5 is a box diagram of the application software according to the invention; 
     FIGS. 6, 7 and 8, respectively, illustrate lexical analysis, a symbol chart, and parsing; and 
     FIGS. 9, 10 and 11 are flow charts for several modes of operation of the chemical calculator according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, the reference numeral 1 denotes a control processing unit (CPU) such as an Intel 8088, optionally fitted out for speed of computation, with a floating point unit (FPU), such as an Intel 8087. 
     A random access memory 2 (RAM) provides for program execution using data from a storage unit 3, a diskette drive, say. 
     A data entry device 4, such as a keyboard, is also provided. The data entry device could equally well be a bar code reading system, or other device actuable to cause the CPU to perform its several functions with respect to RAM 2, storage unit 3, and a display device 5, which may be a CRT, LCD screen, or the like. Not shown, but optionally provided, could be a printer and/or interconnection with other computers and/or networks. 
     In actual practice, the chemical calculator, according to FIG. 1, may be housed in a simple housing (not shown) although FIG. 2 can be supposed to represent a plan view, to scale, of such housing, say roughly 6&#34;×8&#34;×2&#34;-3&#34;. 
     As FIG. 2 shows, the calculator keyboard for the most part will be made up of an array or field 6 of element keys corresponding in number to the elements to be represented thereby, in this case 108, which are arranged in a periodic table of elements configuration, and each key is labeled with the atomic number and conventional alphabetic symbol of one of the elements. In this case, the configuration is one wherein the rare earth element keys are grouped just below the main body of elements. 
     In the lower right of the Figure, function keys F1 through F10, and so labeled, along with suitable mnemonics corresponding to the previously described &#34;modes&#34;, an ENTER key, and five keys numbered S1, S2, S3, S4 and S5, provide a mode or function key pad 7. Also, keys S1, S2, S3, S4, and S5, are provided for special functions, and keys F8, F9, and F10, which have no mnemonics, can provide for customized function modes utilizing special database and calculation functions. For example, it is presently contemplated that keys F8 and F9 will provide isotope and m/e Modes 7 and 8, respectively, as described under Summary of the Invention, supra. 
     Just to the left of the key pad 7, an array of 12 keys provides an edit key pad 8. Nine of the keys have mnemonic labels indicating conventional editing functions, but three are labeled only E1, E2, and E3. These three provide for additional editing capabilities related to future use needs. 
     To the left of key pad 8 an array of 20 keys provides the functions of a conventional numerical key pad 9, such as is found on most terminal and personal computer keyboards. 
     At the lower left, is a shift key labeled 2nd, and below it are four keys each mnemonically labeled with pairs of mathematical functions of scientific interest, and providing a scientific function key pad 10. The shift key provides for selecting the upper or lower functions, as need be. 
     Just above the mathematical function key pad 9 are cursor screen control keys mnemonically labeled to indicate Home, direction, and the like, again all as commonly found on terminal and personal computer keyboards. 
     At the left of element key array 6, a column of keys, downwardly labeled 1 through 9, provides for selecting group properties of element periods (rows of elements). 
     Finally, the topmost keys in the columns of element keys are numbered 1 through 18 and provide for selecting properties of groups or &#34;families&#34; of elements. Thus, starting at the left of the array 6, keys 1 and 2 are also labeled 1A and 2A; 3 through 7 are labeled 3B through 7B; 8, 9, and 10 have the common label 8B; 11 and 12 are 1B and 12B; and 13 through 18 are 3A through 7A. 
     In addition, it is evident from FIG. 2 that in general there is room for addition of some keys. For example, in element field 6, there is a space between the Uns and Une elements 107 and 109, for an element 108, and to the right of the Une key there is room for up to nine more keys corresponding to elements 110 and up, which so far are undiscovered, or at least not acknowledged. 
     The calculator, according to the invention, can also take the form shown in FIG. 3 wherein instead of being a unitary assemblage, it utilizes presently available calculator hardware, and the data entry features of the FIG. 2 calculator. 
     Thus, in FIG. 3, a calculator 12, such as the previously-referred to Hewlett Packard HP48SX, and a data entry device 13 corresponding to data entry device 4 of FIG. 1, and having the format shown in FIG. 2, but lacking display 11, are connected via a suitable interface 14. It should be noted that calculators like the HP48SX are ordinarily equipped with a means for connecting them to external data entry devices, such as bar code readers, etc., and are built around microprocessors programmable by means of &#34;cards&#34; inserted in the interior of the calculator. In other words, the HP48SX differs from the present invention only in respect of data entry arrangement. The HP48SX has a display which would serve for display 11. 
     An alternative to pressing the element symbol on a key pad or board would be to provide a bar code reader. Thus, as shown in FIG. 4, the reader 15 is pointed at the element symbol square for beryllium. The square contains the bar code for &#34;Be&#34;, and the reader is aimed at the bar code for reading it into the calculator. Another alternative (not shown) would be a screen display configured by software as the periodic table in the format shown in FIG. 3, and which would be accessed by light pen, &#34;mouse&#34;, or equivalent. 
     While the data entry device 4 has thus far been described as a specialized device, the calculator will be like conventional personal computer systems in having software to control the operation of the calculator. When the calculator is turned on a copy of the software is loaded into memory and from then on the CPU uses those instructions and the user input to decide what action to take. 
     The software used in the calculator can be divided in three separate layers: BIOS, DOS and Application. 
     BIOS contains the basic instructions used by the CPU to display data on the screen, to access the Storage Unit and to receive the user input from the keyboard. They are included with the CPU/Memory modules. This is conventional and no further description is necessary. 
     DOS is the so called Operating System. It takes control of the CPU and does the necessary tasks to load the Application software. In a regular computer it is also used to do other tasks such as creating, modifying and deleting files. In the calculator its tasks will be much more limited. It is conventional, and the user will never interact with DOS during normal operation of the calculator, so no further description is necessary. 
     Application is the actual program in charge of providing the unique functions available in the calculator. It is divided into several modules as shown in the box diagram of FIG. 5, wherein the labels in the boxes, Parser, Screen Driver, Database Manager, and Keyboard Driver, briefly describe the functions of and denote the modules. 
     Parser is the heart of the software. It contains the rules defining the Chemical Functions to be provided by the calculator, and calls for the Lexical Analyzer to retrieve the user input, i.e., chemical element symbols, mathematical symbols, etc. When it needs a datum about a specific chemical element it calls the Database Manager. Once it has determined the result of a Chemical Function it calls the screen driver to display the data. FIG. 6 illustrates the parsing operation. 
     Screen Driver&#39;s main function is to cause the display 11 to display the results of calculations as defined by the Parser. It will also echo back the user input, i.e., if the user presses the symbol for helium, the screen driver will display &#34;He&#34; on the screen. 
     Database Manager contains all the data related to the chemical elements. It accepts requests from the Parser about a specific element and returns the necessary information to the Parser. 
     Lexical Analyzer serves as a filter/translator to the Parser. When the Parser requests some input, it must call the Lexical Analyzer. The Lexical Analyzer then calls the Keyboard Driver and, as shown in FIG. 7, translates the user input into the appropriate chemical element and other symbols as shown in FIG. 8. 
     Keyboard Driver&#39;s function is to accept the user input (key presses) and pass the characters to the Lexical Analyzer for translation. 
     FIG. 9 illustrates Mode 1, i.e., one presses the key marked F2, &#34;Elem&#34;, and then a single key in the field 6, causing the display of the element symbol marked on the former key, along with a listing of data associated with that element: atomic weight, atomic number, and/or other data such as may be obtained from a periodic table chart such as that shown on the inside back cover of the well-known and ubiquitous CRC Handbook of Chemistry and Physics, 49th Edition 1968-1969 (hereinafter CRC Handbook). 
     More particularly, the database fields in the current calculator include, for each element of the periodic table, the following data: 
     1. Symbol 
     2. Name 
     3. Atomic number 
     4. Atomic mass 
     5. Electron configuration 
     6. Crystal structure 
     7. Property of oxide of element 
     8. Physical state of element 
     9. Covalent radius 
     10. Atomic radius (ionic radius) 
     11. Atomic volume 
     12. Ionization potential 
     13. Specific heat 
     14. Thermal conductivity 
     15. Heat of fusion 
     16. Heat of vaporization 
     17. Electronegativity 
     18. Electron affinity 
     19. Electrical conductivity 
     There is superficial resemblance here to merely getting the same material by inspection from the CRC Handbook and/or other such sources. However, in the present invention, the keyboard is laid out and marked with element symbols and atomic numbers like the CRC Handbook table, but the latter&#39;s confusing jumbles of other data have been eliminated, thereby allowing one not only to easily locate the desired element symbol without the distracting graphics accompanying those symbols in the CRC Handbook table, but to retrieve, without human error, the data represented by those graphics, since once the correct element is chosen, nothing is left to the vagaries of human visual inspection and selection of data. 
     In Mode 2, the user presses the key marked F3 &#34;PAIR&#34;, and then two element keys. As shown in FIG. 10, the element symbols are displayed, as in the Mode 1 case, but this time a calculation is made, about some relation between the two elements, such as bond length or electronegativity difference. 
     Turning to Mode 3, the display 11 (an LCD screen, say) indicates that a user of the calculator has used it in Mode 3, i.e., has pressed the key marked F4, &#34;FORM&#34;, in FIG. 2, and then keyed in the appropriate alphabetic, numeric and syntactical symbols in the arrangement known as &#34;aluminum sulphate&#34;, the conventional formula for which is displayed at the bottom of display 11. 
     The software causes the CPU to analyze the conventional formula into its parts. Thus, as shown in FIG. 11, the software causes the CPU to break the formula, as keyed in, down to its individual elements, Al, S, O and H. The CPU also gets the numerical values of the atomic weights of Al, S, O and H from the database manager. Pressing F4, &#34;FORM&#34;, invokes the parser&#39;s algorithmic capacity for summing up the atomic weight total for 2Al, 3S, 120, 5H, 2.50 0, to wit, 387.17615. In effect, the parser takes the multipliers from the lexical analyzer, gets the individual atomic weights from the database manager and performs the summation of 2Al+3S+14.5O+5H=Formula Weight. 
     The foregoing procedure is superficially analogous to using the above CRC Handbook. But, at page B-173 thereof, where the physical constants of some aluminum compounds are tabulated, only the unhydrated sulphate, and a natural occurring hydrate with 18 H 2  O are listed. Moreover, even if the 2.5 H 2  O hydrate were listed, the formula weight would be given by CRC to only two decimal places, whereas in the present invention, the weight is given by the calculator according to the invention automatically and error-free, to five decimal places. 
     The foregoing explanations of Modes 1, 2 and 3 in terms of FIGS. 9, 10 and 11 obviate such explanation of the other Modes 4 et al in view of the calculation examples set forth above under Background of the Invention, and of the descriptions of said other modes set forth under Summary of the Invention, supra. 
     N.B. In claims the term &#34;chemical calculations&#34; means deriving formulae, balancing chemical reactions, and/or the like. In other words, the sort of calculations set forth in detail hereinabove.