What is an atom? How do the subatomic particles reside within the atom? What are valence electrons?

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An atom is the basic unit of a chemical element and the fundamental building block of all matter. Every atom consists of a dense central nucleus surrounded by a cloud of electrons. The nucleus contains protons and neutrons, while electrons orbit around it in specific energy levels or shells. Atoms are made up of three main subatomic particles. Protons carry a positive charge and are located in the nucleus. Neutrons have no charge and are also found in the nucleus alongside protons. Electrons carry a negative charge and orbit around the nucleus in specific energy levels or electron shells. Electrons do not orbit randomly around the nucleus. Instead, they occupy specific energy levels called electron shells or orbitals. The first shell, called K shell, can hold a maximum of 2 electrons. The second shell, L shell, can hold up to 8 electrons. The third shell, M shell, can accommodate up to 18 electrons. Electrons fill these shells from the innermost to the outermost, with higher shells having higher energy levels. Valence electrons are the electrons located in the outermost electron shell of an atom. These electrons are extremely important because they determine how atoms bond with each other, control the chemical reactivity of elements, and influence many properties of elements. For example, carbon has 4 valence electrons in its outer shell, which allows it to form four chemical bonds with other atoms. To summarize what we have learned about atoms: Atoms are the fundamental building blocks of all matter, consisting of a nucleus containing protons and neutrons, surrounded by electrons in energy shells. Valence electrons in the outermost shell are crucial for determining how atoms interact and bond with each other. This understanding of atomic structure forms the foundation for all of chemistry and much of physics.