We explain what an atom is and how each of its parts is made up. Also, its history, studies about it and what a molecule is.
What is an atom?
It is known as an atom the smallest unit that makes up matter.
The word atom comes from ancient Greek (atom“without division”) and was coined by the first philosophers to theorize about the composition of things, that is, the elementary particles of the universe. Since then, with the emergence of atomic models, the way we imagine them has varied enormously, as one atomic model succeeded the previous one over the centuries, until reaching the one we use today.
the atoms have the properties of the chemical element they make up and, in turn, the elements are organized and classified according to their atomic numbers, electronic configuration and chemical properties in the Periodic Table of the elements.
The same chemical element can be composed of different atoms of the same class, that is, with the same atomic number (number of protons that each atom in the element has), although their atomic masses are different.
For example, there are different atoms of the same element that differ in their number of neutrons, and they are called isotopes. A representative case is the isotopes of the element carbon (12C, 13C, 14C). Then, each atom belongs to the same chemical element or not, depending on its number of protons, so atoms with the same number of protons belong to the same chemical element.
How is an atom composed?
the atoms are composed of a nucleus and one or more electrons (which have a negative charge) around it. The nucleus is made up of particles called protons and neutrons. Protons have a positive charge and neutrons are neutral. The set of protons and neutrons are called nucleons.
Protons and electrons are attracted to each other by the electromagnetic force (interaction between charged particles with electric and magnetic fields), while protons and neutrons are attracted to each other by the nuclear force (force experienced only by the particles that make up the atomic nucleus).
How do atoms combine?
the atoms can combine with each other to form chemical bonds which happens when they share their electrons in one way or another. Chemical bonds can be covalent, ionic and metallic, which gives rise to covalent molecular compounds, ionic networks or metallic compounds (although it is important to clarify that no chemical bond is absolutely covalent or ionic). In this way, atoms can combine to form simple molecules such as water, as well as to form complex macromolecules such as proteins, DNA, and RNA.
Although the atoms They are distinguished from each other thanks to the configuration of their particles it is also true that all atoms of the same element are exactly identical: the hydrogen atoms in the Sun are the same as those that make up our body, and the carbon atoms in the body of a dog are identical to those that make up a diamond The difference is in the way in which atoms are combined to constitute the different chemical compounds that make up the organs and organ systems in living beings, the materials generated in industry, and all the matter that makes up the universe.
Parts of an atom
Atoms are made up of two essential parts:
- The core. Around 99.94% of the mass of an atom is concentrated in the nucleus, where the protons and neutrons (which together are called “nucleons”) are held together by strong nuclear forces, which prevents the protons from They repel each other, as they have the same electric charge.
- Atomic orbitals An orbital describes a region of space surrounding the atomic nucleus in which the probability of finding an electron is very high. These regions have different shapes that are obtained as a result of solving the stationary Schrödinger equation. Erwin Schrödinger was an Austrian scientist who developed this equation in 1925 to calculate the evolution of a subatomic particle, such as electrons. Thus, the electrons form a kind of “cloud” around the nucleus, which is represented by the shape of the atomic orbitals. On the other hand, each atomic orbital corresponds to a certain energy value for electrons, so they are organized according to their energy values. The following figure shows the shapes of the first atomic orbitals:
history of the atom
The first to formulate the idea of the existence of atoms was the Greek philosopher Democritus (5th-6th centuries BC) from purely imaginary speculations (as science was understood at that time).
His studies were taken up by later philosophers such as Leucippus and Epicurus, but he was ignored during the Middle Ages, overshadowed by the creationist explanation of the world, which attributed everything to God.
We had to wait until 1773 when the French chemist Antoine de Lavoisier postulated his theory on the neither creation nor destruction of matter (it is only transformed) or Law of conservation of mass, which allowed John Dalton to formulate the first modern atomic theory in 1804.
Successive physics and chemistry scholars were inspired by his work to propose better and more complex systems for understanding the fundamental particles of matter. Subsequently, new atomic models were proposed until reaching the most used ones today.
The currently accepted structure is that derived from Rutherford's experiments in 1911, together with the formulations of Niels Bohr, Schrödinger and Heisenberg.
Molecule
It is known as a molecule the joining of two or more atoms through chemical bonds to form a more complex and electrically neutral structure. Chemical bonds can be covalent or ionic.
The molecules can be made up of atoms of the same chemical element For example, the oxygen molecule (O2), or by atoms of different chemical elements, for example, the glucose molecule. Monatomic gases, for example, helium (He), are also considered molecules.
