The smallest particles involved in chemical changes.

Atomic diameters are on the order of 10⁻¹⁰m.

experiment

A molecule is a whole made up of atoms that are bonded together according to a certain bonding order and spatial arrangement. This bonding order and spatial arrangement is called a molecular structure. Due to the interactions between atoms within the molecule.

The first person to propose a more precise concept of molecules was the Italian chemist Avogadro, who published his molecular theory in 1811

The average molecular diameter is on the order of 10⁻¹⁰m

Electron is the earliest elementary particle discovered. It is commonly represented by the symbol e. It is negatively charged with a charge of 1.602176634×10-19 Coulombs. It is the smallest unit of charge and has a mass of 9.10956×10-31kg.

Discovered in 1897 by British physicist Joseph John Thomson while studying cathode rays.

Electrons on the metal plate split into spinons and holes as they jumped onto the wire through quantum tunneling.

Atomic nucleus, referred to as "nucleus", is located at the core of an atom and consists of two particles, protons and neutrons. Protons are composed of two up quarks and one down quark, and neutrons are composed of two down quarks and one up quark.

The nucleus is extremely small, its diameter is between 10-15m~10-14m

In 1912, the British scientist Rutherford conducted an experiment based on alpha particles bombarding gold foil. Most of the alpha particles still moved in the original direction. A few alpha particles were greatly deflected due to impacting electrons. Some alpha particles deflected more than 90°. Some alpha particles deflected more than 90°. The deflection direction of alpha particles is even close to 180° due to hitting the nucleus. This experimental fact confirmed that the atom contains a small but massive positively charged center. This is the origin of the atomic nucleus model.

A proton is a subatomic particle with a positive charge of 1.6 × 10-19 Coulombs (C)

Diameter is about 1.6~1.7×10−15m

In 1919, Rutherford conducted an experiment using alpha particles to bombard nitrogen nuclei. The experimental device is as shown in the figure. There is radioactive material A in container C. The alpha particles emitted from A are shot onto the aluminum foil F. The thickness of the aluminum foil is appropriately selected. , after the container C is evacuated, the α particles are absorbed by F and cannot pass through. Place a fluorescent screen S behind F, and use a microscope to observe whether there is flash on the fluorescent screen. After passing nitrogen into C through valve T, Rutherford observed a flash from the fluorescent screen S. When he replaced the nitrogen with oxygen or carbon dioxide, no flash was observed. This indicates that the flash must be caused by alpha particles hitting the nitrogen nucleus. Caused by new particles passing through the aluminum foil.

subtopic

The neutron is an uncharged elementary particle with a rest mass of 1.6748×10-27kg. Its radius is about 0.8×10-15m, which is similar to the size of a proton. Neutrons are commonly represented by the symbol n. The spin quantum number of a neutron is 1/2.

In 1932, British physicist Chadwick discovered neutrons in an experiment using alpha particles to bombard beryllium.

Quark (English: quark) is a basic particle that participates in strong interactions and is also the basic unit of matter. Quarks combine with each other to form a composite particle called a hadron. The most stable hadrons are protons and neutrons, which are the building blocks of atomic nuclei. Due to a phenomenon called "quark confinement," quarks cannot be directly observed or separated, and can only be found in hadrons. For this reason, most of what humans know about quarks comes indirectly from the observation of hadrons.