Volume 2 Chapter 1 Build Menu DRAW

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ELEMENT TYPES

Function

These options are used to specify the element type of an atom.

Remarks

The "Current Element" is the default element assigned to newly generated atoms. It is always displayed in the bottom right-hand corner of the menu box which contains element symbols.

You can change the Current Element as follows:

(i)
select one of the 8 most common elements in the database viz. C, N, O, S, P, Cl, Br, F.

(ii)
select OTHER to replace the BUILD menu by the PERIODIC-TABLE sub-menu, then select the appropriate element or element group.

(iii)
select the Current Element box, then type the new element symbol.

Note that, in MOVE mode, if the element symbol of a selected atom is different from the Current Element symbol then the atom selected is assigned the Current Element symbol.

Example

On entry to the BUILD menu the current element type is carbon.

This is indicated - see below - by the symbol C in the second red box down on the right hand side.

The 8 most common elements, excluding H, in the database are C, N, O, S, P, Cl, Br, F. These symbols are displayed in lines a and b.

To change the element type from the default C to N

The various group and period symbols in the PERIODIC-TABLE sub-menu are given in Appendix 1. To remind users of the special groupings:

8B = 8X + 8Y + 8Z

TR = 1R + 2R + 3R + Ac

LN = La, Ce, Pr, ... ,Yb, Lu

AN = Ac, Th, Pa, ... ,No,Lw

1M = 1A + 2A

2M = Al, Ga, In, Tl, Ge, Sn, Pb, Sb, Bi, Po

3M = 1M + 2M

4M = 1M + 2M + LN + AN + TR

HD = H or D

AA = any element.

Note that by clicking in the current element box and responding to the prompt, the PERIODIC-TABLE sub-menu can be bypassed and any element, group or ELDEF (see later) symbol may be typed.

If the groups of elements explicitly afforded by the PERIODIC-TABLE sub-menu are not adequate then the user can set up special groups using the ELDEF feature. This will be illustrated by two examples.

Ex. 1 Suppose we wish to build the fragment, where RR = Se or Te:

Then we might build the fragment:

Ex. 2 Suppose we wish to build the fragment (i) - see below.

We could proceed as in Ex. 1 but we will, instead, use the minus (-) feature of ELDEF.

Then we might build the fragment (ii).

You should note the following points relating to the use of ELDEF:

(a)
The new element symbol can be one or two characters:

the first must be alphabetic

the second must be alphabetic or a blank character.

(b)
In the same session you can use more than one new element symbol e.g. MM, NN, OO, PP, RS, etc.

Suppose you have defined MM and at a later stage you select OTHER. When the PERIODIC-TABLE sub-menu appears on the screen then the new element box containing MM is displayed.

If you define a new element NN then a second new element box will appear, containing NN.

Note, however, that you cannot re-use a symbol in a later new element definition. Thus, suppose we have defined MM and then later we select OTHER.

(c)
If you find that in many sessions you are using the same set of ELDEF's then you should consider saving them using the STORE-FRAGMENT command in the FILES menu.

There is no need to have a fragment on the screen - simply generate your ELDEF's, then

  • Select TO-FILES

    Select STORE-FRAGMENT

    VAX/VMS users should read the appropriate notes in Appendix 12.

Each time you begin a session and want to retrieve these ELDEFs:

  • Select TO-FILES

    Select FETCH-FRAGMENT

Currently in the VAX/VMS version, the ELDEF-containing fragment appears on the FETCH-FRAGMENT display as a blank box. However, if this box is selected, the ELDEFs are written into the BUILD OTHER display and can be selected and used in the current session.

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Volume 2 Chapter 1 Build menu EXIT.