I 1789 skrev den franske kemiker [[Antoine Lavoisier]] ''[[Traité Élémentaire de Chimie]]'', som bliver betragtet som den første moderne [[lærebog]] om [[kemi]]. Lavoisier definerede et element som en substans, hvis mindste enheder ikke kunne nedbrydes til mindre substans.<ref>Lavoisier with Robert Kerr, trans. (1790) ''Elements of Chemistry''. Edinburgh, Scotland: William Creech. [https://babel.hathitrust.org/cgi/pt?id=gri.ark:/13960/t5v735k9h;view=1up;seq=30 From p. xxiv:] "I shall therefore only add upon this subject, that if, by the term ''elements'', we mean to express those simple and indivisible atoms of which matter is composed, it is extremely probable we know nothing at all about them; but, if we apply the term ''elements'', or ''principles of bodies'', to express our idea of the last point which analysis is capable of reaching, we must admit, as elements, all substances into which we are capable, by any means, to reduce bodies by decomposition. Not that we are entitled to affirm, that these substances we consider as simple may not be compounded of two, or even of a greater number of principles; but, since these principles cannot be separated, or rather since we have not hitherto discovered means of separating them, they act with regard to us as simple substances, and we ought never to suppose them compounded until experiment and observation has proved them to be so."</ref> Lavoisiers bog indeholdt en liste over "simple substanser" som Lavoisier mente ikke kunne nedbrydes yderligere, hvilket inkluderede [[oxygen]], [[nitrogen]], [[hydrogen]], [[fosfor]], [[kviksølv]], [[zink]] og [[svovl]], hvilket dannede grundlag for den moderne over grundstoffer. Lavoisiers liste inkluderede også '[[lys]]' og '[[caloric]]', som man på dette tidspunkt mente var et materielt stof. Hans klassificerede disse substanser som metaller og ikke-metaller. Mens mange ledende kemikere nægtede at tro på Lavoisiers nye teori, så blev hans værk udbredt blandt den yngre generation. Lavoisiers beskrivelse af grundstoffer mangler dog fuldstændig, da han kun klassificerede dem som metaller og ikke-metaller.
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