Molecular Structure.
Atoms, electrons, neutrons and protons

Atom

Atom

What is an atom? Imagine you have a piece of iron. The parts. You still have two pieces of iron but smaller ones. You turn them back, again ... Each time you will have smaller pieces until a moment will come, in which if you return them to leave, what you would have left would no longer be iron.

At this point what remains is an atom, an atom of iron.

Definition of atom

In a more formal way, we define atom as the smallest particle in which an element can be divided without losing its chemical properties.

The origin of the word atom comes from the Greek, which means indivisible. At the time these particles were baptized, it was believed that they could not really be divided, although today we know that atoms are made up of even smaller particles, distributed in the two parts of the atom, the so-called subatomic particles.

Parts of an atom

Definition of atom

The structure of an atom is very simple. We distinguish two parts of an atom: nucleus and cortex.

The nucleus is the central part of the structure of the atom. In the part of the nucleus are protons (particles with positive charge) and neutrons (particles without electric charge).

In the crust, the outer part of the atom is the electrons (particles with negative electric charge).

Protons, neutrons and electrons are the subatomic particles that make up the structure of the atom. What differentiates one atom from another is the relationship established between them.

Electrons, negatively charged, are the lightest subatomic particles. The positively charged protons weigh about 1,836 times more than the electrons. Neutrons, the only ones that have no electrical charge, weigh approximately the same as protons.

Protons and neutrons are grouped in the central part of the atom formed by the atomic nucleus. For this reason they are also called nucleons.

In this way, the central part of the atom, the atomic nucleus, has a positive charge in which almost all its mass is concentrated, while in the foreshortening around the atomic nucleus there is a certain number of electrons, negatively charged. The total charge of the atomic nucleus (positive) is equal to the negative charge of the electrons, so that the total electric charge of the atom is neutral.

Bohr model

This description of the electrons orbiting the atomic nucleus corresponds to the simple Bohr model. According to quantum mechanics, each particle has a wave function that occupies all the space and the electrons are not located in orbits although the probability of presence is higher at a certain distance from the nucleus.

Properties of atoms

The basic units of chemistry are atoms. During chemical reactions the atoms are conserved as such, they are not created or destroyed, but they are organized differently creating different bonds between one atom and another.

Atoms are grouped forming molecules and other types of materials. Each type of molecule is the combination of a certain number of atoms linked together in a specific way.

According to the composition of each atom, the different chemical elements represented in the periodic table of the chemical elements are differentiated. In this table we can find the atomic number and the mass number of each element:

  • Atomic number, it is represented by the letter Z, it indicates the quantity of protons that has an atom, which is equal to that of electrons. All atoms with the same number of protons belong to the same element and have the same chemical properties. For example all the atoms with a proton will be of hydrogen (Z = 1), all the atoms with two protons will be of helium (Z = 2).
  • Mass number, it is represented by the letter A, and it refers to the sum of protons and neutrons that the element contains. Isotopes are two atoms with the same number of protons, but different numbers of neutrons. The isotopes of the same element have chemical and physical properties very similar to each other.

Periodic table of elements. Characteristics of atoms.

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Last review: October 28, 2016

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