All substances around us are discrete, that is, they consist of separate small "bricks". Most people know two types of these "bricks": molecules and atoms. Is a molecule the smallest particle of matter? This issue is considered in the article.
Question about the structure of matter
Before turning to the answer to the question of whether the molecule is the smallest particle of matter and why, if yes or no, it is useful to consider the emergence of the very concept of discreteness of matter.
The modern achievements of science owe much to the teachings of ancient Greek philosophers. The issue of the structure of matter surrounding us is no exception. Many sources indicate that Democritus, observing the sparks that occur when rubbing amber with fur, suggested the existence of elementary particles that form matter. Subsequently, he developed his doctrine, which is now commonly called atomistic. The word "atom" from ancient Greek is translated as "indivisible".
It is important to emphasize two features here: firstly, Democritus did not independently think of the existence of atoms, many ideas of this teaching belong to his mentor; secondly, there is historical evidence that back in the 15th century in India there was a similar doctrine of the discreteness of matter, that is, 1000 years before the birth of Democritus!
The atomic doctrine of the structure of matter was not accepted in Antiquity (it is known that the famous ancient Greek philosopher Aristotle rejected this concept), and in the Middle Ages the question of the structure of matter was not even raised, since at that time science had practically not developed. They remembered the atom only in the New Age, and then the concept of the "molecule" appeared.
The "appearance" of a molecule
The famous Italian physicist Amedeo Avogadro in the 18th century, studying the behavior of gases, came to the conclusion that they did not consist of atoms, but of larger formations, for which he used the name "molecule". This term can be translated from the Latin language as "small mass", that is, a particle forming a substance. Based on the meaning of the name itself, one can answer positively to the question of whether the molecule is the smallest particle of matter. However, this will be wrong! It is interesting to draw an analogy with the name "atom", because it is also not "indivisible".
Modern ideas about molecules
According to the modern definition, a molecule is an electrically neutral and stable group of at least two atoms that are interconnected by strong chemical bonds (covalent, ionic). It is important to add to this definition the property of molecules to combine into massive bodies due to weak forces (van der Waals interactions, hydrogen bonds).
Examples of molecules are water (H 2 O), oxygen (O 2 ), a protein molecule, DNA, and many others. Previously, they also spoke about monatomic molecules (noble gases), but now this concept is practically not used, since a monatomic molecule is a simple atom.
Also, the concept of "molecule" does not include crystalline and amorphous structures. For example, in the case of a metal crystal, it is not customary to talk about a molecule. This concept is mainly used in biology and organic chemistry when talking about proteins, fats and carbohydrates.
A molecule is not the smallest particle of matter!
Why is not a molecule the smallest particle of matter? Because it consists of atoms, therefore the atom is the smallest unit of matter. For example, water in the form of a liquid consists of H 2 O molecules, but the molecule itself consists of one oxygen atom and two hydrogen atoms.
In nature, there are many examples of substances that are not formed by molecules. In fact, these are many solid materials of inorganic chemistry: metal (steel), covalent (diamond), ionic (table salt) crystals.
In turn, most liquids (water, alcohol, gasoline) and gases (carbon dioxide, methane) are molecular structures, that is, their smallest “brick” is the corresponding molecule.
Curiously, in many forums, people respond positively to the question of whether a molecule is the smallest particle of matter. Why? This answer refers to the fact that the molecule retains the properties of a particular substance, if it is divided into these "bricks". This answer is incorrect, since the properties of bulk matter in many respects depend not only on the molecules (if any) that comprise it, but also on the interaction between them. For example, a single water molecule does not have the same physical properties that a mole of water molecules will exhibit. Moreover, with a decrease in the geometric dimensions of the system, quantum effects begin to play an important role.
Is an atom the smallest unit of matter?
After the question was examined that molecules are really the smallest particles, but they are not the smallest structural units of matter, it is interesting to note that although the atom plays the role of the smallest particle of matter, it is still not “indivisible”.
Many people know that atoms are made up of protons, neutrons, and electrons. Some also know that protons or neutrons, in turn, are made up of quarks. Then it turns out a quark - an elementary particle of matter?
The answer to this question cannot be unequivocal. So, scientists know the elementary particles of the class of leptons, the smallest of which is the neutrino, but the neutrino does not form matter. An electron also belongs to leptons, its energy is much less than the energy of any quark, therefore, in terms of energy, it can be considered an elementary particle of matter. Nevertheless, the question is complicated by the existence of some modern physical theories (for example, the theory of superstrings), in which hypotheses are made about the existence of even smaller “bricks” of matter.