The 5 differences between atoms and molecules

Matter is everything that has mass and occupies a volume in space. And from the subatomic level to observing the Universe as a whole, the matter of the Cosmos is organized in different levels closely related to each other.

For a long time, we believed that atoms were the smallest units of matter, as they were considered indivisible and extremely small. In fact, a single grain of sand is made up of more than 2 million million atoms. The same number of galaxies as there are in the Universe.

And although we discovered that there was a lower level (the subatomic), this level of subatomic particles was governed by different rules of the game: the laws of quantum mechanics. For this reason, atoms, despite not being the lowest level of organization of matter, are the basic unit of matter.

But, What relationship do these atoms have with molecules? They're synonyms? What is the difference between them? If you want to find answers to these and many other questions about the atomic and molecular nature of the Universe, you have come to the right place. In today's article we will see the main differences between atoms and molecules.


    What are atoms? And the molecules?

    Before going deep into analyzing their differences in the form of key points, it is interesting (and also important) to understand exactly what atoms and molecules are. Therefore, let us explore the nature of these two levels of organization of matter that are so related but at the same time so different.

    Atom: what is it?

    An atom is the smallest unit in which stable matter can be obtained, maintaining the chemical properties of a chemical element in question.. In other words, atoms are each of the pieces that make up the puzzle of molecules. And here we are already seeing the relationship between them.

    We have all seen the famous periodic table of the chemical elements. In it, the (for now) 118 discovered elements appear and are arranged, which are, in essence, each of the ingredients of the known matter in the Universe.

    Everything that exists is a combination of these elements. Each element has unique properties and interacts with other elements in a unique way. But what do atoms have to do with this? Well basically everything.

    And is that a chemical element is an atom with a specific number of protons. That is, depending on the number of protons in the atomic nucleus, we will have one element or another. Thus, hydrogen, the lightest and most abundant element in the Cosmos, has only one proton in its nucleus. If the atom has 6 protons, then we are dealing with carbon. And so with the 118 elements.

    An atom, then, is a structure that is at the limit of the quantum world with a nucleus that represents only one thousandth of its total size but that houses 99.99% of its mass. This nucleus is made up of two types of subatomic particles: protons and neutrons.

    Protons are composite subatomic particles (made up of three quarks, which are elementary subatomic particles) with a positive charge and a mass 2,000 times greater than that of the electron. The number of protons determines the chemical element. And, under normal conditions, the number of protons is equal to that of neutrons, the other subatomic particles of the atomic nucleus and that they are similar to protons with the particularity of not having an electrical charge. Protons and neutrons are stuck together through strong nuclear force.

    And around this nucleus, we have the electrons. Some elementary subatomic particles that orbit around protons and neutrons following undefined orbits, but are governed by the crazy principles of quantum physics. An electron is, simultaneously, in all the places where it can be.

    Either way, electrons are particles 2,000 times smaller than protons that have a negative charge and are attached to the nucleus through the electromagnetic force (one hundred times less intense than the strong nuclear force). Imagine an atom as something the size of a football field. Well, the nucleus would be a tennis ball in the center of the field and the electrons, the head of a pin in one corner. 99.99999% of the atom is empty.

    Molecule: what is it?

    Molecules are organizations of atoms. It is a higher level of organization of matter in which each molecule has unique properties that arise from the characteristics of the different atoms that make it up and, therefore, from the chemical elements that make it up.

    In other words, a molecule is a defined and ordered grouping of atoms that constitutes the smallest unit of a pure substance capable of preserving its properties. There are molecules made up of a single atom (such as helium), but the most common is that they are combinations of two (such as hydrogen H2) of three (H2O), of four (NH3), of five (CH4), etc.

    The variety of molecules in the Universe is simply unimaginable. There are billions of different molecules, as there are almost infinite (it is to say) ways in which atoms can join each other and form stable bonds. Water, for example, is a molecule that is born from the union, through a covalent bond (the strongest type of bond that exists), of two hydrogen atoms and one oxygen atoms.

    When these molecules are made up of atoms of at least two different chemical elements, we speak of a compound. And if, in addition, one of these elements is carbon, we are talking about an organic molecule. If it does not have carbon, it is an inorganic molecule.

    Later, these molecules can organize among themselves to give rise to macromolecules (such as DNA or proteins) necessary for the existence of living beings. And these macromolecules organize themselves to give cells. And the cells to give tissues. And the tissues, to give organs. And so on.

    In summary and in a more technical way, a molecule is an electrically neutral group, a sufficiently stable level of organization of matter that arises from the union of at least two atoms linked to each other through strong chemical bonds.

    How is an atom different from a molecule?

    After analyzing both concepts individually, surely the differences between atoms and molecules have been more than clear. Anyway, in case you want the most visual information, we have prepared a selection of the main differences between them in the form of key points.

    1. The atomic is a lower level of organization of matter

    The lowest level of organization of matter is the subatomic level. After this we find the atomic level. And after this comes the molecular level. As we can see, while the level of atoms is the second of the 19 levels of organization of matter, the molecular is the third. The atom is a deeper level of structuring of matter. And it is that more than anything, atoms are, as we have seen, the smallest unit in which stable matter can be obtained.

    2. Molecules are the result of the union of atoms

    Surely the most important difference. Atoms are atoms; whereas molecules are sets of atoms. Atoms are the result of the union, through the strong nuclear force, of protons and neutrons in a nucleus and of, through the electromagnetic force, electrons orbiting around this nucleus.

    Molecules, on the other hand, are stable groups of at least two atoms linked together through strong chemical bonds. In this sense, the main difference between both concepts is that molecules are made of atoms and atoms are made of subatomic particles.

    3. Molecules are bigger than atoms

    A very little technical difference but one that will surely help you understand it. And the fact is that molecules, being the result of the union of atoms, are, logically, larger than these atoms. Cesium (atomic number 55) is the chemical element whose atoms are largest. Cesium atoms are 343 picometers in size (p.m). A picometer is equal to one billionth (one million million) of a meter.

    Instead, the largest molecule ever synthesized (PG5) is 10 nanometers in size. A nanometer is one billionth of a meter. The difference is, although not seem, abysmal.

    4. The diversity of atoms is less than that of molecules

    Actually, of different atoms there are only 118. What are the chemical elements of the periodic table. Now, these 118 different chemical elements, by being able to combine with each other in very different ways, allow the diversity of molecules to be immense. Sea believes that the diversity of molecules could be of the order of 160 billion, although all are estimates. We have about 90 million different molecules registered.

    5. In molecules there are chemical bonds; in the atoms, no

    And finally, a very important difference. While molecules are the result of the bonding of atoms through chemical bonds (such as covalent bonding), the components of atoms do not bond to each other through bonds. Protons, neutrons and electrons do not establish bonds, but are held together through two of the four fundamental forces (electromagnetism and strong nuclear force). Namely, cohesion in molecules is due to chemical bonds; cohesion in atoms, to elemental forces.

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