Atom | Definition, Structure, History, Examples, Diagram, & Facts ...
2024年12月11日 · All atoms are roughly the same size, whether they have 3 or 90 electrons. Approximately 50 million atoms of solid matter lined up in a row would measure 1 cm (0.4 inch). A convenient unit of length for measuring atomic sizes is the angstrom (Å), defined as 10 −10 metre.
Atomic physics | Structure, Particles & Energy | Britannica
Through the procedures of wave mechanics, the energies of atoms in various energy states and the characteristic wavelengths they emit may be computed from certain fundamental physical constants—namely, electron mass and charge, the speed of light, and Planck’s constant.
Atom - Development, Theory, Structure | Britannica
2024年12月11日 · Studies of the properties of atoms. Size of atoms; Electric properties of atoms; Light and spectral lines; Discovery of electrons; Identification of positive ions; Discovery of radioactivity; Models of atomic structure. Rutherford’s nuclear model; Moseley’s X-ray studies; Bohr’s shell model; The laws of quantum mechanics; Schrödinger’s ...
atom - Kids | Britannica Kids | Homework Help
The tiny particles called atoms are the basic building blocks of all matter. Atoms can be combined with other atoms to form molecules, but they cannot be divided into smaller parts by ordinary means. The word atom comes from the Greek word atomos, meaning “indivisible.” The ancient Greeks were the first to think of the atom as the basic ...
atomic model - Encyclopedia Britannica
His atomic model essentially consisted of solid spheres of different sizes for different types of atoms. The Greek atomic theory is significant historically and philosophically, but it was not based on observations of nature, measurements, tests, or experiments.
Periodic table | Definition, Elements, Groups, Charges, Trends,
2024年11月10日 · As atoms have more electrons, they have more orbits available to fill, and thus the rows contain more elements farther down in the table. Why does the periodic table split? The periodic table has two rows at the bottom that are usually split out from the main body of the table.
Atom - Electrons, Orbitals, Energy | Britannica
2024年12月11日 · Each element has a unique set of energy levels, and so the frequencies at which it absorbs and emits light act as a kind of fingerprint, identifying the particular element. This property of atoms has given rise to spectroscopy, a science devoted to identifying atoms and molecules by the kind of radiation they emit or absorb.
Atom - Electrons, Nucleus, Bonds | Britannica
2024年12月11日 · Atom - Electrons, Nucleus, Bonds: Once the way atoms are put together is understood, the question of how they interact with each other can be addressed—in particular, how they form bonds to create molecules and macroscopic materials.
Molecule | Definition, Examples, Structures, & Facts | Britannica
2024年11月23日 · Molecule, a group of two or more atoms that form the smallest identifiable unit into which a pure substance can be divided and still retain the composition and chemical properties of that substance. Learn more about the properties and structures of molecules in …
Electron | Definition, Mass, & Facts | Britannica
electron, one of the three basic subatomic particles—along with protons and neutrons—that make up atoms, the basic building blocks of all matter and chemistry. The negatively charged electrons circle an atom’s central nucleus, which is formed by positively charged protons and the electrically neutral particles called neutrons.