atom
smallest particle of an element that retains its identity in a chemical reaction
the Greek philosopher Democritus
what Greek philosopher was among the first to suggest the existence f atoms, and believed that atoms were indivisible and indestructible?
John Dalton, an English chemist and schoolteacher
the modern process of discovery regarding atoms began with whom?
different
Atoms of any one element are ? from those of any other element.
physically
Atoms of different elements can form ? by combining in whole-number ratios.
seperated, joined, or rearranged
Chemical reactions occur when atoms are?
never true
atoms combine in one-to-one ratios to form compounds
always true
Atoms of one element are different from atoms of other elements
scanning tunneling microscope
an instrument used to generate images of individual atoms
100,000,000
how many copper atoms would you have to line up side by side to form a line 1 m long?
divisible
what are atoms known today as?
subatomic particles
what can be broken down into even smaller, more fundamental particles?
electrons, protons, and neutrons
what are the three kinds of subatomic particles?
J.J. Thomson, English physicist
who discovered the electron?
electrons
negatively charged subatomic particles
J.J. Thomson
experiments that invlved passing electric current thrugh gases at low pressure
electrodes
J.J. Thomson sealed the gases in glass tubes fitted at both ends with metal disks called?
electrodes
were connected to a source of electricity
anode
which electrode became positively charged?
cathode
which electrode became negatively charged?
glowing beam, or cathode ray
traveled from the cathode to the anode
opposite charges
do opposite or same charges attract?
Robert A, Millikan, U.S. physicist
carried out experiments to find the quantity of charge carried by an electron.
mass of the electron
what did Millikan calculate?
one unit or negative charge and its mass is 1/1840 the mass of a hydrogen atom
how much does an electron carry?
by using a magnet, and by using electrically charged plates
Thomson examined two way that a cathode ray can be deflected, what were they?
particles of matter
what are electric charges are carried by what ?
TRUE
electric charges always exist in whole-number multiples, no fractions
electrically neutral particle
when a given number of negatively charged particles combines with an equal number of positively charged particles, what is formed?
yes
does a positive charge remain when a typical hydrogen atom loses an electron?
Eugen Goldstein
who observed a cathode-ray tube and found rays traveling in the direction opposite to that of the cathode rays?
canal rays; positive particles
what did he call these rays that traveled in the direction opposite to that of the cathode rays?
proton
what has a mass about 1840 times that of an electron?
English physicist James Chadwick
who confirmed the existence of yet another subatomic particle: the neutron?
neutrons
what subatomic particles has no charge but with a mass nearly equal to that of a proton?
Rutherford
who tested mostly relative massive alpha particles?
Rutherford
who said "This is almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you?
Rutherford
who proposed that the atom is mostly empty space, thus explaining the lack of deflection of some of the alpha particles?
nucleus
what is the tiny central core of an atom and is composed of protons and neutrons?
nuclear atom
the Rutherford atomic model is known as what?
electron
what subatomic particle is distributed around the nucleus and occupies almost all the volume of the atom?