Elements, John Dalton, 1808 28 στοιχεία είναι γνωστά στο πέρασμα προς τον 19 αιώνα, οπότε ο Dalton επαναδιατυπώνει την ατομική θεωρία Elements are made of tiny particles called atoms. The atoms of a given element are different from those of any other element, and the atoms of different elements can be distinguished from one another by their respective relative atomic weigh/mass. All atoms of a given element are identical. Atoms of one element can combine with atoms of other elements to form chemical compounds, and a given compound always has the same relative numbers of types of atoms. Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process, and a chemical reaction simply changes the way atoms are grouped together.