2.2. Atomic Structure: Subatomic Particles

One of the most fundamental and essential topics for understanding chemistry is atomic structure. Understanding this structure is crucial to understanding how atoms combine to form molecules and chemical compounds. Let's dive into the wonderful world of subatomic particles: protons, neutrons and electrons.

The atom is the smallest unit of a chemical element that retains the properties of that element. It is made up of three types of subatomic particles: protons, neutrons, and electrons. Each of these particles has distinct characteristics that make them unique.

Protons: are subatomic particles with a positive charge. They are located in the nucleus of the atom, along with the neutrons. The number of protons in an atom determines the element's atomic number. For example, hydrogen has one proton, so its atomic number is 1. The number of protons in an atom also determines the element's identity. For example, all atoms with 6 protons are carbon atoms.

Neutrons: are uncharged subatomic particles, that is, they are neutral. They are also located in the nucleus of the atom. The number of neutrons in an atom does not affect the identity of the element, but it does affect the isotope of the element. Isotopes are atoms of the same element with different numbers of neutrons. For example, hydrogen has three isotopes: hydrogen (no neutrons), deuterium (one neutron), and tritium (two neutrons).

Electrons: are subatomic particles with a negative charge. They orbit the nucleus of the atom in regions called shells or energy levels. The number of electrons in an atom is usually equal to the number of protons. However, atoms can gain or lose electrons through chemical reactions, forming ions. Ions are atoms or molecules that have a net charge due to the gain or loss of electrons. For example, a sodium atom can lose an electron to form a positively charged sodium ion (Na+).

The atomic structure is the basis for understanding the periodic table, the formation of chemical compounds, chemical reactions and many other concepts in chemistry. Atomic structure is also the basis for quantum theory, which explains the behavior of atoms and subatomic particles.

In short, atomic structure is one of the foundations of chemistry. Understanding subatomic particles and how they interact to form atoms is crucial to understanding chemistry and physics. Therefore, it is essential for any student preparing for the ENEM exam to have a solid understanding of this topic.

This e-book is designed to provide a clear and concise understanding of atomic structure and subatomic particles. It will cover the basics as well as more advanced concepts to help you prepare for the ENEM exam. With this e-book, you will be well equipped to understand chemistry and succeed in the ENEM test.

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5Atomic Structure: Atomic Number and Mass Number

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