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Quinn Science K4

Introduction to Atoms

QuestionAnswer
atomos indivisible
Democritus 440 BC Greek philosopher proposed the idea that there was an uncuttable part of matter, single material, small, hard, different shapes, and sizes. The parts join together to make different materials
Dalton British chemist and teacher late 1700's, experimented, atoms are small particles cannot be created, ,divided, or destroyed, atoms of the same element are the same and different elements are different, atoms join together to make new substances
Aristotle Greek philosopher 384 - 322 BC disagreed with Democritus
Thomson 1897 British scientist, cathode-ray experiment, discovered smaller particles, now called electrons
Rutherford 1909 tested Thomson's idea with the gold foil experiment, 1911 he cam up the the new model that has a small, dense, positively charged nucleus, with a lot of empty space that electrons travel around like planet around the sun
Bohr 1913 Danish scientist that worked with Rutherford, suggested electrons travel in definite paths a certain distance from the nucleus
Modern model Schrodinger and Heisenberg exact path of electrons are not known but there are regions they are likely to be found
radioactive unstable atom whose nucleus can change composition
ion when the number of electrons do not equal the number of protons, it becomes a charged particle, happens when bonding with another atom
atom the smallest particle into which an element can be divided and still be the same substance
theory a unifying explanation for a broad range of hypotheses and observations that have been supported by testing
electron negatively charged particle found in electron clouds with mass 1/1840 AMU, involved in the formation of chemical bonds
model representation of an object of system
nucleus tiny extremely dense, positively charged center of an atom made of protons and neutrons
electron cloud region in an atom that electrons are likely to be found, also called electron levels
proton positvely charged, in the nucleus, with mass 1 AMU, is equal to the atomic number that determines the identity of an element
atomic mass unit the SI unit used to express that masses of particles in atoms
neutron in the nucleus, no charge, with mass 1 AMU
atomic number number of protons in the nucleus of an atom
isotope atoms that have the same number of protons but different numbers of neutrons comparing to atoms of the same element
mass number the sum of the protons and neutrons in an atom
atomic mass the weighted average of the masses of all the naturally occurring isotopes of an element
weak force important in radioactive atoms, plays a key roll when a neutron can change into a proton or electron
strong force keeps the nucleus together, greater than the electromagnetic force
electromagnetic force opposite charges that attract each other, holds electrons around the nucleus
gravitational force all objects experience it, and is due the masses and distance between two objects
atoms are neutral because they have the same number of positive protons and negative electrons
Plum pudding model Thomson's idea that negative particles are scattered throughout positive material
Created by: cquinnd15.org