law of conservation of mass
In a chemical reaction, matter is neither created nor destroyed (Antoine Lavoisier)
law of definite proportions
All samples of a given coupound, regardless of their source or how they were prepared, have the same proportions (mass ratio) of their constituent elements (does not have to be whole number proportions) (Joseph Proust) (For example, the mass ratio of wate
law of multiple proportions
When two elements, A and B, combine to form more than one compound (AB1, AB2, AB3, etc), the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole numbers (John Dalton)
atomic theory
The theory that: 1. each element is composed of tiny indestructible particles called atoms, 2. that all atoms of a given element have the same mass and other properties, and 3. that atoms combine in simple, whole-number ratios to form compounds (John Dalt
cathode rays
a stream of electrons produced when a high electrical voltage is applied between two electrodes within a partially evacuated tube
cathode ray tube
a partially evacuated tube with two electrodes between which a high electrical voltage is applied
electrical charge
a fundamental property of certain particles that causes them to experience a force in the presence of electrical fields
electron
a negatively charged, low mass particle found outside the nucleus of all atoms that occupies most of the atom's volume but contributes almost none of its mass
radioactivity
the emission of subatomic particles or high-energy electromagnetic radiation by the unstable nuclei of certain atoms
nuclear theory
the theory that most of the atom's mass and all of its positive charge is contained in a small, dense nucleus (Ernest Rutherford)
nucleus
the very small, dense core of the atom that contains most of the atom's mass and all of its positive charge; it is composed of protons and neutrons
proton
a positively charged subatomic particle found in the nucleus of an atom
neutron
an electrically neutral subatomic particle found in the nucleus of an atom, with a mass almost equal to that of a proton
atomic mass unit (amu)
a unit used to express the masses of atoms and subatomic particles, defines as 1/12th the mass of a carbon atom containing six protons and six neutrons
atomic number (Z)
the number of protons in an atom; it defines the element
chemical symbol
a one- or two-letter abbreviation for an element that is listed directly below its atomic number on the periodic table
isotope
atoms of the same element with the same number of portons but different numbers of neutrons and consequently different masses
natural abundance
the relative percentage of a particular isotope in a naturally occurring sample with respect to other isotopes of the same element
mass number (A)
the sum of the number of protons and neutrons in an atom
ion
at atom or molecule with a net charge caused by the loss or gain of electrons
cation
a positively charged ion
anion
a negatively charged ion
periodic law
a law based on the observation that when the elements are arranged in order of increasing mass, certain sets of properties recur periodically (Dmitri Mendeleev)
metal
a large class of elements that are generally good conductors of heat and electricity, malleable, ductile, lustrous, and tend to lose electrons during chamical changes
nonmetal
a class of elements that tend to be poor conductors of heat and electricity and usually gain electrons during chemical reations
metalloid (semimetal)
a category of elements found on the boundary between the metals and nonmetals of the periodic table, with properties intermediate between those of both groups; several of them are classified as semiconductors
semiconductor
a material with intermediate electrical conductivity that can be changed and controlled
main-group elements
those elements found in the s or p blocks of the periodic table, whose properties tend to be predictable based on their position in the table
transition elements/metals
those elemtns found in the d block of the preiodic table whose properties tend to be less predictable based on their position in the table
family/group
columns within the main group elements in the periodic table that contain elements that exhibit similar chemical properties
noble gases
the group 8A elements, which are largely unreactive (inert) due to their stable filled p orbitals
alkali metals
highly reactive metals in group 1A of the periodic table
alkaline earth metals
fairly reactive metals in group 2A of the periodic table
halogens
highly reactive nonmetals in group 7A of the periodic table
atomic mass/weight
the average mass in amu of the atoms of a particular element based on the relative abundance of the various isotopes; it is numerically equivalent to the mass in g/mol
molar mass
the mass in grams of one mole of atoms of an element; numerically equivalent to the atomic mass of the element in amu
mass spectrometry
an experimental method of determining the precise mass and relative abundance of isotopes in a given sample using an insrument called a mass spectrometer
mole (mol)
a unit defined as the amount of material containing 6.022 X 10^23 (Avogadro's number) particles
Avogadro's number
the number of carbon-12 atoms in exactly 12g of carbon-12; equal to 6.022 x 10^23
J.J. Thomson
discovered the electron, determined that it had a negative charge, and determined its charge-to-mass ratio using the Cathode Ray Tube Experiment
Robert Millikan
determined the magnitude of the electron's negative charge using the Oil Drop Experiment
Ernest Rutherford
discovered the nucleus and the proton using the Gold Foil Experiment; proposed the nuclear theory
James Chadwick
discovered the neutron
Dmitri Mendeleev
proposed the periodic law and created the periodic table of elements
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