If the energy of an atom is increased (for example. B when a substance is heated), the energy of the electrons in the atom is also increased, i.e. the electrons are stimulated. In order for the excited electron to return to its original energy or soil state, it must release energy. One of the ways an electron can release energy is by emitting light. Each element emits light with a frequency (or color) specific to the heating corresponding to the energy of electronic stimulation. An envelope of electrons can be conceived as an orbit, followed by electrons around an atomic nucleus. Since each hull can only hold a fixed number of electrons, each hull is connected to a certain range of electronic energy, so each hull must be fully filled before the electrons can be added to an outer shell. The electrons in the extreme shell determine the chemical properties of the atom (see The Valencia shell). To explain why electrons exist in these shells, see the configuration of electrons. The existence of electron shells was observed experimentally for the first time in the X-ray absorption studies of Charles Barklas and Henry Moseley. [non-primary source required] Barkla labelled them with the letters K, L, M, N, O, P and Q. The origin of this terminology was alphabetical. A series “J” has also been suspected, although subsequent experiments suggest that K absorption lines are generated by the most intimate electrons.
These letters later corresponded to values 1, 2, 3, etc. They are used in the spectroscopic notation of the victory track. Helium is generally considered chemically inert. This is due to its extremely stable and closed electron configuration, its affinity of zero electrons and the highest ionization energy of all elements. In the case of hydrogen atoms that have only one electron, the power of the network on the electron is as great as the electrical attraction of the nucleus. However, when more electrons are involved, each electron (in the shell n) feels not only the electromagnetic attraction by the positive nucleus, but also the forces of rejection of other electrons in shells ranging from 1 to n-1. As a result, the net electrostatic force on the electrons in the outer shells is significantly lower. Therefore, these electrons are not as strongly bound as electrons that are closer to the nucleus. Each hull consists of one or more sub-hulls, themselves composed of atomic orbitals.
For example, the first shell (K) has a shell called 1s; the second (L) shell has two subseeds, called 2s and 2p; the third shell has 3s, 3p and 3d; The fourth hull has 4s, 4p, 4d and 4f; the fifth hull has 5s, 5p, 5d and 5f and can theoretically fit more in the 5g subcup that is not occupied in the configuration of electrons in the ground condition of a known element.  The different possible sub-shells are presented in the following table: the list below corresponds first to the principle of structure. However, there are a number of exceptions to the rule. For example, unlike other atoms, palladium (atomic number 46) has no electrons in the fifth hull. Some entries in the table are uncertain if experimental data are not available. (For example, after 108, the elements have a half-life so short that their electron configurations have not yet been measured.) The metal materials are formed by atoms with metallic properties, in which the valenz-bol cartridges flow freely. Metals have been the dominant material for structural applications in the past. They are extremely good conductors of heat and current, are not transparent for visible light and have high stiffness, mechanical resistance and thermal stability. Some common metals are aluminum, copper, iron, magnesium, zinc, nickel and titanium. Because of their superior properties, alloys are more often used in structural applications than pure metals.
Alloys are materials with metal properties containing two or more chemical elements, at least one of which is metallic.