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What is an atom?

What Is An Atom Everything around us is made up of atoms. The air we breathe, the land we inhabit, and even our bodies are made of it. It is a term derived from the Latin atŏmus and the Greek atomon, where a means without and atoms: section, which is literally interpreted as: which cannot be cut, which is indivisible.

The term was proposed by the Greek philosophers Democritus and Leucippus. In the 5th century BC, Leucippus argued that there was only one kind of matter and that if it was cut into smaller and smaller pieces there would come a time when it could no longer be cut, this which Democritus called atoms, because they had no division. .

the atom

atom definition

More formally, the atom can be defined as the structure in which matter is organized and its smallest constituent unit.

The concept of atom dates back to antiquity, more precisely to the 5th century BC. It was the Greeks Democritus and Leucippus who gave this name to the smaller, indivisible particles which, when combined, create matter.

The structure in which all matter is organized is called an atom. It is the smallest and most stable particle into which an element can be split without losing its chemical properties.

Atoms form molecules when grouped together, and in turn are made up of smaller particles called subatomic particles which are distributed in two parts of the atom, where the electrons, protons and neutrons are, taking into account because electrons are subatomic particles with negative charges, protons have a positive charge and neutrons have no charge.

atom size

1650504970 707 What Is An Atom The regular sizes of an atom are about 22 h, that is, one ten billionth of a meter. Until now, atoms do not have well-defined limits regarding their size, so there are different ways to define their size.

parts of an atom

Atoms can be divided into two parts, namely: the nucleus and the shell, which in turn have subdivisions.


It is estimated that about 99.94% of the mass of an atom is in the nucleus. It is the central part of the atom, considered its heart. It is composed of neutrons and protons, called nucleons, the former have a neutral charge and weigh the same as electrons, that is, they have no charge, and protons have a charge positive and weigh 1836 times more than electrons.

Neutrons and protons are held together by nuclear energy, so the nucleus will always have a positive charge in which the greatest mass is concentrated, which is equal to the negative charge of the electrons, resulting in an electric charge neutral throughout the atom. When the number of protons in an atom differs from the number of neutrons, it is called isotopes.

Is formed by:


They have a positive electrical charge.


They have no net electrical charge. However, they are present in the atomic nucleus of all atoms except protium (the most common stable isotope of hydrogen).


Also called electron cloud or atomic cloud, it is the region that surrounds the atomic nucleus and in which electrons orbit. It is also known as an electron cloud because it is in this part of the atom that electrons orbit, forming a cloud. Composed only of negatively charged particles. Electrons become the lightest particles in the atom.


They are those which have a negative electric charge and which, by electromagnetic interaction, join the nucleus of the atom.

Nuclear properties of the atom

  • It has been observed that during chemical reactions the atoms remain as they are, that is to say that they are neither created nor destroyed, but that they create different bonds from one atom to another in sequence. organize differently.
  • Atoms stick together and thus form molecules. The combination between a varied number of atoms bonded to each other in a specific way gives rise to a type of molecule.
  • The chemical elements are differentiated by the composition of each atom, defined by the atomic number and the mass number of each element, which in turn are represented in the table of elements.
  • They are not created or destroyed in chemical reactions, but they can create different bonds between atoms.
  • Its composition makes it possible to differentiate the chemical elements within the periodic table, where each element has a mass number and an atom number that identifies it. The mass number represented by the letter A is the result of the sum of neutrons and protons of an element, and the atomic number, represented by the letter Z, is the total number of protons of an atom, which is the same as electrons.
  • It has chemical properties that can be classified based on its valence number, weight, and other physical characteristics.
  • They are distinguished from each other by the configuration of their particles, however, the atoms belonging to the same element are identical.

Atomic number

Indicates the number of protons present in each atom; Keep in mind that the number of protons will always equal the number of electrons. The atomic number of an atom is represented by the letter Z.

mass number

It is the one that refers to the sum of protons and neutrons present in an element and in the periodic table it is represented by the letter A.

types of atoms

What Is An Atom As you already know, atoms are made up of neutrons, protons and neutrons, being in turn the smallest structural unit of matter.

The type of atom we find will be defined by the number of protons it has; so far we can see 118 different types of atoms (found in the periodic table) ranging from hydrogen to oganesson.

One could say that there are as many atoms as protons in its nucleus. For example, all atoms with a proton in their nucleus are often called hydrogen atom, unlike atoms with a total of 29 protons, it is called a copper atom.

natural atoms

Those found in nature in the normal way. Among these are 98 elements, of which gold, silver, copper and noble gases are found in a pure form, that is, they are 100% natural, while d Other elements, such as alkali metals (group 1 elements, except hydrogen) and group elements, called alkaline earths, combine with atoms of other elements, forming chemical compounds.

Artificial or synthetic atoms

It is these elements that do not occur naturally because they are created by complex processes, either through nuclear fusion or through the use of particle acceleration equipment. These elements are generally very unstable radioactive, which is why their production is rare and quite expensive.

So far this type of atoms can be found in the periodic table giving a total of 20, among which we find:

  • einsteinium
  • fermium
  • Mendelevium
  • nobelium
  • Borium
  • Flerovium
  • tenesco
  • Among others.

characteristic of the atom

  • It is the basic unit of chemistry.
  • It has a strong tendency towards stability.
  • They are characterized by their extreme lightness, the approximate mass of electrons being less than 9.1 x 10-28 and that of neutrons and protons 1.675 x 10-24.
  • It obeys the Lewis octet rule.
  • They are indestructible and unalterable. Each atom retains its structural characteristics, this is seen during chemical reactions, where they are never destroyed or created, they only organize themselves differently, giving rise to bonds between one atom and another.
  • When grouped together, they form molecules and materials of different types with different physico-chemical characteristics. Molecules interact to create gases, solids and liquids.
  • Responsible for all the chemical reactivity of atoms are electrons.
  • It is the component of all matter, so everything that exists physically is made up of atoms.
  • They can turn into ions when they lose or gain electrons.
  • Several atoms bonded together form molecules.
  • It is composed of three substructures: electrons, protons and neutrons. Neutrons and protons constitute the nucleus of the atom while the electrons continue to orbit around this nucleus.
  • The greatest mass of the atom is in the nucleus.
  • In an element, all its atoms are identical.

Electron Configuration (April 29, 2022) What is an atom?. Retrieved from
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Electron Configuration - What is an atom?. [Internet]. [Accessed April 29, 2022]. Available from:
"What is an atom?." Electron Configuration - Accessed April 29, 2022.
"What is an atom?." Electron Configuration [Online]. Available: [Accessed: April 29, 2022]
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