135 lines
4.4 KiB
TeX
135 lines
4.4 KiB
TeX
% Example drawings to help explain the VSEPR atom model to high school
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% students. Although the actual model is three dimensional, these drawings
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% are deliberately presented as two dimensional to gently introduce them to the
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% concepts, before advancing to three dimensional models.
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%
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% Authors: Berteun Damman & Arne Röhrs
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\documentclass{article}
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\usepackage{verbatim}
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\begin{comment}
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:Title: Atoms and orbitals
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Example drawings to help explain the `VSEPR atom model`_ to high school
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students. Although the actual model is three dimensional, these drawings
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are deliberately presented as two dimensional to gently introduce them to the
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concepts, before advancing to three dimensional models.
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.. _VSEPR atom model: http://en.wikipedia.org/wiki/VSEPR_theory
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\end{comment}
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\usepackage{tikz}
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\usepackage[version=3]{mhchem}
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\pgfdeclarelayer{background}
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\pgfdeclarelayer{foreground}
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\pgfsetlayers{background,main,foreground}
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% For black & white suggestions are black!95 for the electron
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% and a white background, or a simple shade for the orbitals.
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\colorlet{electron}{blue!75}
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\tikzset{orbital/.style={thick,draw=blue,fill opacity=.60}}
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% Styles for orbitals with 0, 1 and 2 atoms respectively.
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\tikzset{orbital 0/.style={orbital,fill=blue!25}}
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\tikzset{orbital 1/.style={orbital,fill=blue!66}}
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\tikzset{orbital 2/.style={orbital,fill=blue}}
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\tikzset{atomcore/.style={shape=circle,thick,draw=red!40,minimum size=7mm,
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font=\large\color{red!70!gray},fill=red!20,inner sep=0pt}}
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\def\orbheight{1.2}
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\def\orbwidth{.6}
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% Parameters: #1 Rotation of the orbital
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% #2 Coordinate where the orbital should be attached
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% #3 Number of electrons to draw in the orbital
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\newcommand{\orbital}[3]{
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\begin{scope}[rotate=#1,shift=(#2)]
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% These points define the curve for the orbital.
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\coordinate (c1) at (-\orbwidth, .6 * \orbheight);
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\coordinate (c2) at (-\orbwidth, \orbheight);
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\coordinate (c3) at (\orbwidth, \orbheight);
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\coordinate (c4) at (\orbwidth, .6 * \orbheight);
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\coordinate (top) at (0,\orbheight);
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%Coordinates of the electrons
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\coordinate (e1) at (0, 0.45*\orbheight);
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\coordinate (e2) at (0, 0.75*\orbheight);
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\end{scope}
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% These are drawn on a background layer, so orbitals
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% can overlap without covering the electrons, which
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% visualises the role electrons play in chemical bonds.
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\begin{pgfonlayer}{background}
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\draw[orbital #3] (#2) .. controls (c1) and (c2) .. (top) ..
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controls (c3) and (c4) .. (#2);
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\end{pgfonlayer}
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% Draw the electrons
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\ifnum#3>0
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\foreach \n in {1,...,#3} {
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\shade[ball color=electron] (e\n) circle (1mm);
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}
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\fi
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}
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% This allows to quickly place an atom.
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% Parameters: #1 (Optional) Name of the center node
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% #2 Text for the center node
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% #3 A list of rotation-angle/anchor/number of electrons
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\newcommand{\Atom}[3][AtomNode]{
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\node[atomcore] (#1) {\ce{#2}};
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\foreach \ang/\anchor/\n in {#3} {
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\orbital{\ang}{#1.\anchor}{\n}
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}
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}
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\begin{document}
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\pagestyle{empty}
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% Note: Cells of matrices cannot contain layered pictures,
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% therefore we use some old-fashioned scopes.
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\begin{tikzpicture}
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\Atom{B}{90/west/2,0/north/1,270/east/0,180/south/1}
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\begin{scope}[xshift=4cm]
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\Atom{H}{0/north/1}
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\end{scope}
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\begin{scope}[yshift=-4cm]
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\Atom{C}{90/west/1,0/north/1,270/east/1,180/south/1}
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\begin{scope}[xshift=4cm]
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\Atom{Cl}{90/west/2,0/north/2,270/east/2,180/south/1}
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\end{scope}
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\end{scope}
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\end{tikzpicture}
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\medskip
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\begin{tikzpicture}
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\Atom{Cl}{90/west/2,0/north/2,270/east/1,180/south/2}
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\begin{scope}[xshift=2.2cm]
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\Atom{H}{90/west/1}
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\end{scope}
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\end{tikzpicture}
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\medskip
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\begin{tikzpicture}
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\Atom{O}{45/north west/2,315/north east/1,225/south east/1,135/south west/2}
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\begin{scope}[xshift=3.0cm]
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\Atom{O}{45/north west/1,315/north east/2,225/south east/2,135/south west/1}
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\end{scope}
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\begin{scope}[xshift=7.0cm]
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\Atom{O}{45/north west/2,315/north east/1,225/south east/1,135/south west/2}
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\begin{scope}[xshift=1.6cm]
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\Atom{O}{45/north west/1,315/north east/2,225/south east/2,135/south west/1}
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\end{scope}
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\end{scope}
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\end{tikzpicture}
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\end{document}
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