2.24. Atomic Structure: Law of Conservation of Charge
Atomic structure is the fundamental pillar of Chemistry and is one of the most important topics to be covered in a complete course for the Enem test. Understanding this structure is crucial to understanding the Law of Conservation of Charge, which allows us to understand how atoms interact to form molecules, and how chemical reactions occur.
To begin with, an atom is the smallest unit of an element that retains the properties of that element. Each atom is composed of a central nucleus, which contains protons and neutrons, and an electron cloud that orbits the nucleus. Protons have a positive charge, neutrons have no charge, and electrons have a negative charge.
The Law of Conservation of Charge, also known as Faraday's first law of electrolysis, states that the amount of electricity that passes through a substance is proportional to the amount of matter that is broken down. In other words, the total electrical charge of an isolated system remains constant regardless of changes that occur within the system.
In practical terms, this means that in all chemical reactions, the total charge on the reactants (the substances that react) must equal the total charge on the products (the substances formed). If an atom loses an electron (a negatively charged particle), it becomes a positive ion or cation. If an atom gains an electron, it becomes a negative ion or anion. However, the total charge before and after the reaction must remain the same.
For example, consider the reaction between sodium (Na) and chlorine (Cl) to form sodium chloride (NaCl). The sodium atom loses an electron to become a Na+ cation, while the chlorine atom gains that electron to become a Cl- anion. The total charge before the reaction is 0 (Na is neutral and Cl is neutral), and the total charge after the reaction is also 0 (Na+ has a +1 charge and Cl- has a -1 charge, so +1 -1 = 0) .
The Law of Conservation of Charge is a powerful tool for predicting the outcome of chemical reactions and for understanding the structure of chemical compounds. For example, we know that water (H2O) must have a total charge of 0 because it is a neutral molecule. So we know that the two hydrogen atoms (H) must offset the charge on the oxygen atom (O).
In summary, atomic structure and the Law of Conservation of Charge are fundamental concepts in chemistry that help explain how atoms form molecules and how chemical reactions occur. Understanding these concepts is essential to succeed on the ENEM Chemistry test and to have a deeper understanding of the world around us.
