To read electronic formulas, it is necessary to understand the structure of the atom. Atoms of all elements consist of a positively charged nucleus and negatively charged electrons that are located around the nucleus. Electrons are at different energy levels. The farther the electron is from the nucleus, the more energy it possesses. The size of the energy level is determined by the size of the atomic orbital or orbital cloud. The electronic layers of atoms are filled with electrons in the order according to the Klechkovsky rule. When filling the orbital shells of an atom, they are more preferable (more energetically favorable), and, therefore, those states are filled earlier for which the sum of the principal quantum number n and the secondary (orbital) quantum number l, i.e. n + l, has a smaller value. s-elements. d-elements.

Content:
- The electronic formula for the distribution of electrons in the orbitals in an atom
- Principles of the formation of the electron shell of an atom

Examples of graphic representations of electronic formulas of atoms:
- I period
- II period
- III period
- IV period
- V period
- VI period
- VII period