An atom and its atomic number are related concepts but refer to different aspects of an element.
Atom: An atom is the smallest unit of an element that retains its chemical properties. It consists of a nucleus, which contains protons and neutrons, and electrons that orbit around the nucleus. Atoms are electrically neutral, meaning the number of protons in the nucleus is equal to the number of electrons surrounding it.
Atomic Number (Z): The atomic number of an element is a fundamental property that defines its identity. It represents the number of protons in the nucleus of an atom. Each element on the periodic table has a unique atomic number, and it determines the element's position in the periodic table. For example, hydrogen has an atomic number of 1, indicating it has one proton in its nucleus, while carbon has an atomic number of 6, indicating it has six protons.
In summary, an atom is the basic unit of an element, consisting of a nucleus and electrons, while the atomic number represents the number of protons in the nucleus of that atom. The atomic number defines the element and determines its placement in the periodic table, whereas the atom is the physical entity that embodies the element.