What is an atom?

 

An atom is the simplest unit of ordinary matter that forms a chemical element. Atoms that are neutral or ionized make up every solid, liquid, gas, and plasma. Atoms are incredibly tiny, measuring around 100 picometers in diameter. Due to quantum phenomena, it is impossible to precisely anticipate their behavior using traditional physics.

Properties

It has three basics subatomic particles, protons, neutrons, and electrons. Proton is positively charged; neutron has no charge and electron has negatively charge. The central part is known as nucleus which is made up of protons and neutrons. Electrons revolve around them, and the number of protons and electrons are always equal in a neutral atom.  When an atom contains more or fewer electrons than protons, it has a negative or positive net charge, and these atoms are known as ions. The path on which electron revolve around the around the nucleus is called orbit/shell or energy levels.

The electromagnetic force attracts an atom's electrons to its protons in the atomic nucleus. The nuclear force attracts protons and neutrons in the nucleus to each other. The electromagnetic force that repels positively charged protons from one another is frequently stronger than this force. Under some conditions, the electromagnetic force repelling the nuclear force gets greater. The nucleus divides in this situation, leaving behind several components. This is a type of nuclear fission.

The atomic number is the number of protons in the nucleus that determines the chemical element the atom belongs to. Copper, for example, is any atom with 29 protons. The number of neutrons in an element determines its isotope. Chemical bonds allow atoms to join with one or more other atoms to create chemical compounds such as molecules or crystals. Most of the physical changes observed in nature are due to atoms' capacity to associate and disassociate. Chemistry is the branch of science that investigates these changes.

Any two atoms having the same number of protons in their nuclei are defined as belonging to the same chemical element. Different isotopes of the same element have the same number of protons but a different number of neutrons. For example, all hydrogen atoms have one proton, but there are isotopes with no neutrons (hydrogen-1, also known as protium), one neutron (deuterium), two neutrons (tritium), and more than two neutrons (tritium). From the single-proton element hydrogen through the 118-proton element Oganesson, the known elements constitute a series of atomic numbers. All known isotopes of elements with atomic numbers greater than 82 are radioactive, while element 83 (bismuth) has such little radioactivity that it is essentially unnoticeable.

The ratio of protons to neutrons, as well as the existence of specific "magic numbers" of neutrons or protons that represent closed and full quantum shells, impact isotope stability. Within the shell model of the nucleus, these quantum shells correspond to a set of energy levels; filled shells, such as the filled shell of 50 protons for tin, bestow remarkable stability on the nuclide. Only four nuclides (hydrogen-2 (deuterium), lithium-6, boron-10, and nitrogen-14) contain an odd number of protons and neutrons among the 252 known stable nuclides.

Because of the nature of quantum mechanics, no single image has been completely satisfactory for visualizing the atom's various characteristics, forcing physicists to explain distinct features using complementary pictures of the atom. The electrons in an atom behave like particles orbiting the nucleus in some ways. In others, the electrons act like waves around the nucleus that are locked in place. Orbitals are wave patterns that explain the dispersion of individual electrons. These orbital features have a significant impact on an atom's behavior, and orbital groups known as shells dictate an atom's chemical properties.

Atomic mass is measured in terms of the atomic mass unit(amu), which is equal to 1/12 of the mass of a carbon-12 atom. Because the mass of an atom is made up of the mass of the nucleus plus the mass of the electrons, the atomic mass unit differs from the mass of a proton or neutron.