ATOMS, MOLECULES, AND IONS Flashcards
proposed the concept of fire, air, water, and earth to explain the composition of matter.
Empedocles (490-435 B.C.)
proposed the existence of a fifth element which he called quintessence.
Aristotle (384-323 B.C)
came up with a theory stating that everything is composed of small indivisible particles which he called atomos.
Democritus (460-370 B.C.)
____ proposed that atoms have fixed weights and definite properties.
John Dalton
’ experiment about the cathode rays helped English physicist
Sir William Crookes
_____ discover the electron in 1897
J.J. Thomson
_____ determined the charge of an electron in 1909.
Robert Millikan
_____ gold-foil experiment helped him elucidate the existence of the nucleus.
Ernest Rutherford’s
_____ suggested that the total energy of an electron is quantized.
Niels Bohr
The _______ of mass states that the mass of the products in a chemical reaction will always be equal to the mass of the reactants.
law of conservation
The ______ states that all the samples of a chemical compound contain all the elements in the same proportion.
law of constant composition
The ________ states that the elements in a compound have a proportion of those chemical compounds that can be expressed in a small, whole-number ratio.
law of multiple proportions
An ____ is a small, indivisible particle considered as the basic unit of matter.
atom
____ are positively-charged particles located inside the nucleus.
Protons
_____ are small, negatively-charged particles that spin around the nucleus.
Electrons