chapter 2: atoms, molecules,, and ions Flashcards
question of whether matter is or isn’t … led to many ….
continuous; experiments
antoine Lavoisier’s experiments resulted in the
law of conservation of mass
law of conservation of mass: mass is neither … nor .. during
gained; destroyed; chemical reactions
law of constant composition: all samples of pure substance have the
same elements in the same proportions by mass
law of multiple proportions: for compounds that are formed by the same elements, the masses of the first element that combine with a certain mass of the second element is always
a ratio of small whole numbers
Democritus proposes matter is … and called the smallest particles of matter…
discontinuous; atoms
(Dalton’s theory) all matter is made up of
atoms
(Dalton’s theory) atom: smallest unit of an element that
retains the properties of the element
(Dalton’s theory) element is made up of one type of …, and the properties of the atoms of an element are ..
atom; identical
(Dalton’s theory) compounds have atoms of
2 or more elements
(Dalton’s theory) the number of atoms in a compound is
the same
(Dalton’s theory) atoms merely…during chemical reactions
rearrange
(Dalton’s theory) explanation of law of constant composition: compounds are always composed of the same
atoms in the same ratios
(Dalton’s theory) explanation of the law of multiple proportions: compounds can be made from the same elements in different ratios in which the ratio of atoms will be
whole numbers
(Dalton’s theory) explanation of law of conservation of mass: in chemical reactions, atoms are merely …., …., and ….; since the number of atoms and the atoms themselves aren’t changing, the mass
rearranged; combined; separated; doesn’t change either
atoms can be … into several different ..
subdivided; subatomic particles
the three major subatomic particles comprising atoms include:
protons, neutrons, and electrons
the manner in which atoms combine and behave is determined by the … and .. of each subatomic particle
number; type
JJ Thomson used a gas discharge tube to show that cathode rays were
electrically charged particles
cathode rays traveled in …. and were deflected by … and …
straight lines; electric and magnetic fields
Thomson determined by the direction of the rays’ deflection that the particles were
negatively charged
electrons:
negatively charged particles
Robert A. Milikan measured the
charge of the electron
(Milikan’s experiment) exposed tiny oil drops to
high-energy radiation
(Milikan’s experiment) measured the rate that the electrically charged oil droplets fell in the
presence/absence of an electric field
(Milikan’s experiment) calculated the … on the oil drop
charge
(Milikan’s experiment) noted that the charge was a multiple of a
single quantity
(Milikan’s experiment) this quantity is the charge of an
electron (e)
with the knowledge of the charge, the … of the electron was measured
mass
in a study meant to analyze deflection of alpha particles as they passed through gold foil, Rutherford recognized that some of the alpha particles were
deflected back toward the source
Rutherford proposed a nuclear model of the atom, which suggested that atoms contain
nuclei of positive charge
nucleus contains most of an atom’s
mass
electrons comprise most of the atom’s
volume
Rutherford found that every element has a different
positive charge
Rutherford suggested the existence of a
proton
the mass of the proton is … times that of the electron
1836
Rutherford was unable to explain why protons were,….., considering that …. between like charges typically exists
close together; repulsion
the existence of a neutral particle was proposed because the proton didn’t account for
the entire nuclear mass
james chadwick discovers
neutrons
neutron’s mass is close to that of a
proton
strong nuclear binding forces hold the particles of nuclei
together
ratio of neutrons to protons is around:
1.0 to 1.6
charges of the electron and proton are equal in
magnitude.
atoms contain equal numbers of
electrons and protons
mass of protons and neutrons are almost equal, while the mass of an electron is
very small
atomic number (Z): amount of .. in an atomic nucleus; … an element
protons; identifies
number of neutrons in atoms of the same element are not always the same:
isotopes
mass number (A): amount of
protons and neutrons in an atom
isotopes have the same … but different ..
atomic number; mass numbers
most elements occur in nature as mixtures of
stable isotopes
about 75% of naturally occurring elements have
2 or more stable isotopes
isotopes disproves one aspect of
Dalton’s atomic theory
to portray specific isotopes, the following notation is used:
a X
z
X→
element’s symbol
a→
mass number
z→
atomic number
the atomic number and element’s symbol do not both have to be included, because either one can
identify the element
ions: charged atoms that are formed when atoms
lose/gain electrons
cation: … formed when an atom … one or more electrons
positive ion; loses
anion: ….; formed when an atom … one or more electrons
negative anion; gains
notation used to identify ions, and notation used to identify isotopes can be
combined
atomic mass unit (u):
1/12 mass of Carbon-12 atom
atomic mass unit is the standard unit to measure
atomic mass
all other atomic masses are compared with the
Carbon-12 standard
1 u =
1.66 x 10-27 kg
masses of neutrons and protons are approximately
1 u
atomic masses of all the elements found with
mass spectrometers
(mass spectrometer) a sample of an element in gaseous form is exposed to a beam of high energy electrons which convert the atoms of the element to
cations
(mass spectrometer) a magnetic field deflects the cations into a
curved path
(mass spectrometer) the degree of curvature determines the
mass and charge of the ion
(mass spectrometer) the charge to mass ratio of the ions is then
calculated
mass spectrometer measures .. and …. of isotopes in a sample of an element
masses; relative abundance
isotopic compositions of most naturally occurring elements are … and aren’t influenced by the … of the sample
constant; origin
isotopic mass: mass of an
isotope of a given element
a weighted average mass can be calculated that considers the
abundance of isotopes
atomic mass: weighted … of the naturally occurring element
average mass
atomic mass is an average: portrays natural isotopic
distribution of an element
classification of elements enables comprehension of
elements’ properties
periodic table arranges the elements into …, with elements of similar properties falling in the same …
rows; column
Mendeleev initially arranged elements by increasing …., although he deviated from this to place elements with similar … together
atomic mass; properties
Mendeleev predicted the existence of other
elements
Moseley ordered the elements based on their
atomic numbers
period: … of the periodic table
horizontal row
properties of elements vary across
periods
groups: …. of the periodic table
columns
properties of elements in the same groups are
similar
numbers associated with rows refer to the outermost … in which electrons can be found in their ground state
energy level
