Atoms and molecules

Water turns to steam when it boils and freezes in winter. Such questions have long interested people: what is inside matter? The Greek scholar Democritus (about 460–370 BCE) thought that everything consists of very small, indivisible particles — atoms; “atom” is Greek for “indivisible”. His work has not survived; his ideas are preserved in other people’s books. Our great ancestor Abu Bakr al-Razi (about 865–925) said that even the atom can be divided: inside it there are voids and moving small parts, and forces act between these parts. Beruni and Ibn Sina discussed the question in letters: Beruni thought that division could be neither “nonexistent” nor “endless”; Ibn Sina said that division has a limit. Today it is proved that the atom has a complex structure: a positively charged nucleus and negatively charged electrons around it; the nucleus is made of protons and neutrons, and these of quarks.