Teachers of physics and chemistry at educational institutions are well aware that it is much easier to explain a topic if you resort to analogies or use approximate examples, explaining “on the fingers”. Although the descriptions given may not fully correspond to the generally accepted model, nevertheless, this approach gives its results. This is exactly the case in atomic physics.
The chemical properties of substances are relatively easy to explain if we use the theory of atomic structure, proposed in 1911 by the English physicist E. Rutherford. Despite the fact that his model is only partially true, this is quite enough to understand the ongoing processes. Today we will talk about what are valence electrons and what is their relationship with the properties of the material under study. But first, recall the planetary model of the structure of the atom.
Rutherford determined that an atom is not an indivisible particle, as previously thought, but consists of a heavy nucleus in the center and electrons rotating around it. The electric charge of the nucleus is positive (+), while electrons, in turn, are negative (-). Eight years after the publication of his theory of atomic structure, Rutherford was able to conduct a unique, at that time, experiment - to turn nitrogen into oxygen. The experiment consisted of “bombarding” nitrogen atoms with alpha particles. After the collision, an oxygen atom formed and an “extra” particle with a positive charge, subsequently called a proton.
The theory has acquired a complete form: the nucleus includes protons, which, using magnetic forces, hold electrons in orbits. Since the atom is electrically neutral, and the proton and electron are attracted, their total amounts are equal. In 1932, physicist J. Chadwick discovered that in addition to protons, there are particles without charge in the nucleus - neutrons. They are responsible for the mass. Depending on the energy of the electron, it can be at different distances from the nucleus. Valence electrons are those negatively charged particles that:
- located at the maximum distance from the core, in outer orbits;
- can interact with neighboring atoms.
By interaction, it is necessary to understand the ability to leave your atomic orbit or change the trajectory of motion.
Valence electrons are determined very simply - according to the periodic table. For basic elements (except for subgroups, since there are exceptions), the condition is true: the maximum number of valence electrons corresponds to the number of the group in which the element under study is located. An atom with a large theoretical amount of such particles is reluctant to give them to other atoms, therefore it is an oxidizing agent (takes away the missing). And, on the contrary, with a small group number, valence electrons are easily given away by the element, entering into interaction. In this case, we are talking about a reducing agent or a donor atom.
Valence electrons directly depend on the state of the atom. So, if one way or another from outside to inform him of additional energy (transfer to an excited state), then the orbits of the valence particles will become more.
Data on the valency of materials allow their active use, predicting the result. For example, chemical sources of electric current based on electrolytes use elements that are capable of sending and receiving electrons. Neutral material would be useless in this case. It is easy to guess that if all the outer electronic shells of an atom are filled, then such an element is chemically neutral and does not enter into interaction with other atoms (or the interaction force is so negligible that it can be neglected). A vivid example of this is inert gases.