Democritus Democritus was an Ancient Greek pre-Socratic philosopher primarily remembered today for his formulation of an atomic theory of the universe. Democritus was born in Abdera, Thrace, around 460 BC, although some thought it was 490 BC John Dalton John Dalton FRS was an English chemist, physicist, and meteorologist. He is best known for proposing […]

alpha decay The disintegration of a nucleus into a nucleus of another element with the emission of an alpha particle, which is a helium nucleus. atomic mass The weighed average mass of an atom of the element in naturally occurring samples; given under its symbol in the period table (in atomic mass units, symbolized u). […]

Subtomic Anything smaller than an atom. ( the particles that make up an atom). Nucleus center of atom, contains protons and neutrons. Protons nucleon with a positive charge. mass of one AMU Neutrons nucleon with no charge. mass of one AMU Electron Subatomic particle with a negative charge Electron cloud area around the nucleus where […]

Absorption Line An isolated bright or dark line in a spectrum produced by emission or absorption of light of a single wavelength. Absorption Line Spectrum The electromagnetic spectrum, broken by a specific pattern of dark lines or bands, observed when radiation traverses a particular absorbing medium. The absorption pattern is unique and can be used […]

Atom Contains a positively charged nucleus made of protons and neutrons, surrounded by negatively charged electrons Size of atom Very small with a radius of 0.000000001m Charge of proton +1 Relative mass of proton 1 Charge of electron -1 Relative mass of electron 1/5000 (negligible) Charge of neutron Relative mass of neutron 1 Charge of […]

classical physics development of physics before 1900 modern physics development of physics after 1900 atomic physics to do with the electrons in an atom discrete matter elements would get to a point where they couldn’t be divided anymore (true) idea of continuous matter you can keep dividing elements forever and ever – Aristotle John Dalton […]

strong nuclear force Fundamental force that holds the nucleus together fusion Process in which smaller nuclei combine to f0rm larger ones neutrons Neutral particles in atoms radioactivity Spontaneous process of nuclei changing by emitting particles or rays electrons Negatively charged particles in atoms beta decay Radioactive decay in which electrons are emitted radioactive isotope Specific […]

Anti-Ballistic Missile or National Missile Defense (ABM or NMD) A system with the ability to destroy enemy missiles or their warheads before they hit their targets. This is usually presented as a “defensive” capability, but it is worth noting that this is a counterforce capability Atom A particle of matter indivisible by chemical means. It […]

nucleus dense, positively charged mass in the center of an atom. proton Positively charged subatomic particle found in the nucleus. neutron Neutral subatomic particle found in the nucleus. atomic number number of protons in the nucleus of an atom. mass number sum of the protons and neutrons in the nucleus of an atom. isotope atoms […]