Science Qz ch. 9 1 & 2 Flashcards
Democritus
proposed matter was made of small particles called atoms.
Aristotle
He did not agree with Democritus, he thought all matter was made up of the four elements.
Dalton
proved Democritus’s theory true, and made the first atomic theory. Also believed that all matter was made up of atoms that were identical, and every element had a unique type of identical atoms.
Thomson
showed that atoms are made of even smaller particles. Discovered negatively charged electrons. Created the chocolate chip cookie model.
Rutherford
Tried the gold foil experiment and discovered protons inside the nucleus. Also concluded atoms are made mostly of empty space.
Chadwick
discovered neutrons working with rutherford.
Bohr
proposed that electrons orbit the nucleus like the solar system, and they farther away the electrons get, the more energy they have.
Proton
positively charged particle inside the nucleus
neutron
neutrally charged particle in the nucleus.
electron
negatively charged particle that orbits the nucleus in layers.
Isotopes
atoms of the same element that have different numbers of neutrons.
Atomic number
the number of protons in an atom of an element (every substance has a different number of protons)
Nuclear decay
a process that occurs when an unstable atomic nucleus changes into another more stable nucleus by emitting radiation.
Alpha decay
releases 2 protons and makes the atomic number decrease by 2.
Beta decay
a neutron changes into a proton, atomic number increases by 1