2.4. Atomic Structure: Electronic distribution

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Atomic structure is a fundamental concept in chemistry and is a crucial part of the ENEM curriculum. Understanding the structure of the atom and how electrons are distributed around the nucleus is essential for understanding chemical reactions, the formation of molecules and the properties of elements.

The atom is made up of three main particles: protons, neutrons, and electrons. Protons and neutrons make up the nucleus of the atom, while electrons orbit around the nucleus in regions known as shells or energy levels. The distribution of these electrons in the energy shells is what we call the electron distribution.

The electronic distribution of an atom can be determined by the atomic number of the element. The atomic number, which is equal to the number of protons in the nucleus of the atom, is also equal to the number of electrons in a neutral atom. For example, hydrogen has an atomic number of 1, so it has one electron. Helium has an atomic number of 2, so it has two electrons.

Electrons are distributed in the energy shells in a specific way. The first shell, or energy level, can contain up to two electrons. The second level can hold up to eight electrons. The third level can also hold up to eight electrons. Subsequent levels have more complex abilities, but for the Enem, we generally focus on the first three levels.

To determine the electronic distribution of an atom, we start by filling the first energy level with up to two electrons. Then we move to the second level, filling it with up to eight electrons. We continue filling energy levels until all electrons have been allocated. For example, carbon has an atomic number of 6, so it has six electrons. The electron configuration for carbon would be 2.4 - two electrons in the first energy level and four in the second.

Understanding electron distribution is crucial to understanding how atoms form bonds and molecules. The electrons in the outermost shell of an atom, known as valence electrons, are those involved in forming chemical bonds. For example, oxygen has an electron configuration of 2.6. That means it has six valence electrons. To reach a more stable state, oxygen tends to form bonds in order to gain two more electrons, thus filling its outer shell.

In summary, atomic structure and electron distribution are fundamental concepts in chemistry. They help us understand how atoms combine to form molecules and how chemical reactions occur. Mastering these concepts is an important step towards doing well on the Enem chemistry test.

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72.5. Atomic Structure: Electronic Configuration