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John Dalton's Atomic Theory
All atoms of a given element were exactly alike and atoms cannot be divided
Bohr's Model of the Atom
This model says that electrons behave more like waves on a vibrating string than like particles.
An electron that is found in the outermost shell of an atom and that determines the atom's chemical properties
The law taht states that the repeating chemical and physical properties of elements change periodicallly with the atomic numbers of the elements
Groups or families
A vertical column of elements in the periodic table (also called family); elements in a group share chemical properties
Atomic Number (Z)
The number of protons in the nucleus of an atom; the atomic number is the same for all atoms of an element.
an atom that has the same number of protons as other atoms of the same element do but that has a different number of neutrons
Atomic mass unit (AMU)
A unit of mass that describes the mass of an atom or molecule; it is exactly one-twelfth of the mass of a carbon atom with mass number 12 (abbreviation,amu)
Avg. atomic mass
the weighted average of the masses of all naturally occuring isotopes of an element
an element or compound that conducts electric current better than an insulator but does not as well as a conductor does.
an element or compound that conducts electric current better than an insulator but does not as well as a conductor does
the SI base unit used to measure the amount of a substance whose number of particles is the same as the number of atoms of carbon in 12 g of carbon-12
the process by which an unstable nucleus emits one or more particles or energy in the form of electromagnetic radiation
the particles that are released from the nucleus during radioactive decay,such as neutrons,electrons,and photons
a positively charged atom that is released in the disintegration of radioactive elements and that constsist of two protons and two neutrons
a charged electron emitted during certain types of radioactive decay,such as beta decay
the time required for half of a sample of a radioactive substance to disintegrate by radioactive decay or by natural processes
the process by which a nucleus splits into two or more fragments and releases neutrons and energy
the quantity of ionizign radiation that does as much damage to human tissue as 1 roentgen of high-voltage X rays does
the process in which light nuclei combine at extremely high temepratures,forming heavier nuclei and releasing energy
a radioactive materail that is added toa substance so that its distribution can be detected later
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