chemical foundations Flashcards
everything is composed of atoms, which are
physically indivisible
between atoms lies
empty space
atoms are
indestructible
Dalton’s Atomic Theory (1808): elements are made of
tiny particles called atoms
all atoms (of the same element) are
identical
atoms of different elements have different
properties
atoms of one element will combine with others to form
compounds
atoms are ______ during chemical reactions, never created or destroyed
rearranged
JJ Thompson (1890s) discovered the electron using the
Cathode Ray Tube
JJ Thompson assumed the existence of
the proton, he knew atoms are usually neutral and the electron (negative charge) needed to be balanced by something
JJ Thompson described the atom as a
Plum Pudding Model (chocolate chip cookie today)
-said the atom was all positive with little charges stuck into it
-the negative could be popped off given the right conditions
Robert Millikan (1909) discovered the
Electron’s charge using the Oil Drop Experiment
Ernest Rutherford (1919) used the
Gold Foil Experiment to postulate the nucleus’s existence
Sir James Chadwick (1932) discovered the
neutron in the nucleus to account for the atom’s missing mass
symbols are used to represent
the elements
subscripts (bottom right) represent
the relative composition of each element in a molecule or compound
superscripts (top right) represent
the charge of an ion
the atom is made of 3 elementary particles:
protons, neutrons, electrons
proton charges are
positive
proton mass is
almost equal to the Neutron
protons are found in the
Nucleus
number of protons is equal to the
atomic number
neutron charges are
neutral
neutron mass is
slightly heavier than the Proton
neutrons are
found in the nucleus
neutron’s purpose:
acts as the glue that holds together the Nucleus
too many/too few Neutrons can result in
nuclear instability and radioactive decay
electron charges are
negative
electron masses are
around 2000 times lighter than the Proton
electron location is
moving around the nucleus around the speed of light