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 Read more…
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 Read more…
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 Read more…
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 Read more…
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 Read more…
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 Read more…
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 Read more…
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 Read more…
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 Read more…
a strong nuclear force Protons and neutrons are held together by what? Atomic number -z- # of protons; defines each element -n- # of neutrons; can vary for each element Mass number -A- Total number of protons -z- and neutrons -n- Isotope the term used to describe different atoms of Read more…
atom basic unit of matter, which consists of a central, positively charged nucleus surrounded by negatively charged electrons Brownian motion the continuous random movement of particles of matter suspended in a liquid or gas cathode-ray tube a vacuum tube containing a source of electrons and a screen to view images Read more…
energy of a photon depends on frequency planks constant the ratio of energy to frequency for a given photon produces photon small packet of electromagnetic energy that has particle-like properties the kinetic energy of a photoelectron depends on wavelength of light in order for a photon to eject an electron Read more…
Radius of atom 10^-10m Radius of nucleus 1/10000 times smaller than atom radius Isotope Same number of protons, different number of neutrons JJ Thompson Plum pudding model Rutherford and Marsden Nuclear model Bohr Energy levels Chadwick neutrons Unstable isotopes decay randomly and emit radiation Activity of a source how quickly Read more…
a. Democritus The ancient Greek who is known for championing the concept of atom was named ______________. a. Democritus b. Socrates c. Plato d. Zeus d. Thomson Who discovered the electron in 1897? a. Dalton b. Bohr c. Rutherford d. Thomson d. Dalton The “billiard ball model” of the atom Read more…
Mass defect Difference in mass between the mass of nucleus and mass of separate nucleons Isotopes Isotopes of elements are chemically identical but have different atomic masses Radiative half life The time it takes for the activity to halve Nuclear Binding Energy the energy released when the nuclide is assembled Read more…
proton the nucleus of the simplest atom- hydrogen. It has a positive charge of +q and a mass of m=1.67×10^-27 kg neutron a particle found in the nucleus that is electrically neutral and that has a mass almost identical to the proton. It was discovered in 1932 by James Chadwick, Read more…
Atoms Atoms contain a positively charged nucleus made up of protons and neutrons.Which is surrounded by negatively charges electrons. How may the energy level of an electron change? – Absorbing electromagnetic radiation moves electrons to a higher energy level, further from the nucleus. – Electromagnetic radiation is emitted when an Read more…
Atomic/proton number Total number of protons in a nucleus. In an uncharged atom this is the number of electrons too. This determins the chemical properties of the element Nucleon/mass number Total number of protons and neutrons in a nucleus. Since electrons have nearly no mass, it also gives the mass Read more…
Dalton’s Atomic Theory ~Matter is composed of extremely small particles called atoms. ~Atoms are indivisible and indestructible. ~Atoms of a given element are identical in size, mass, and chemical properties. ~Atoms of a specific element are different from those of another element. ~Different atoms combine in simple whole-number ratios to Read more…
Atomic Emission Spectra All object emit thermal radiation characterized by a continuous distribution of wavelengths A discrete line of spectrum is observed when a low pressure gas is subjected to an electrical discharge Emission spectroscopy observation of spectral lines atomic hydrogen simplest line spectrum Unique spectra a technique for identifying Read more…