What is an Atom?

An atom is the smallest unit of an element that retains the unique characteristics of that element. Each of the 110 known elements possesses atoms distinct from those of all other elements, giving each its own unique atomic structure. According to the classical Bohr model, an atom is conceptualized with a planetary structure, consisting of a central nucleus encompassed by orbiting electrons, as depicted in Figure 1. The nucleus comprises positively charged protons and uncharged neutrons, while electrons, basic particles with a negative charge, orbit the nucleus.

Atom Structure

Every type of atom is characterized by a specific number of protons, setting it apart from atoms of other elements. For instance, the hydrogen atom, the simplest example, consists of one proton and one electron. Similarly, the helium atom, features two protons and two neutrons in the nucleus, with two electrons orbiting it.

What is an Atomic Number?

All elements are organized in the periodic table based on their atomic number, which equals the number of protons in the nucleus. Hydrogen has an atomic number of 1, while helium has an atomic number of 2. In their neutral state, atoms of a given element have an equal number of electrons and protons, resulting in a net charge of zero, making them electrically balanced.

The Copper Atom

Copper, extensively used in electrical applications, has an atom with 29 electrons arranged in four shells, as depicted in above Figure. Notably, the outermost shell, known as the valence shell, contains only one valence electron. The inner shells are referred to as the core. At room temperature, the valence electron, when provided with enough thermal energy, can break free from the parent atom and become a free electron. In copper, a “sea” of these free electrons exists, not bound to a specific atom but free to move within the copper material. This characteristic makes copper an excellent conductor, facilitating the flow of electrical current.

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