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Ch. 4 Holt
Atoms and the Periodic Table
Term | Definition |
---|---|
nucleus | an atoms central region which is made up of protons and neutrons |
proton | a sub atomic particle that has a positive charge and that is found in the neucleus of an atom |
neutron | a subatomic particle that has no charge and that is found in the neucleus of an atom |
electron | a subatomic particle that has a negative charge |
orbital | a region in an atom where there is a high probability of finding electrons |
periodic law | the law that states that the reapeting chemical and physical properties of elements change periodically with the atomic numbers of the elements |
period | a horizontal row of elements in the periodic table |
group (family) | a verticle column of elements in the periodic table |
ion | an atom or group of atoms that has lost or gained one or more electrons and has a negative or positive charge |
atomic the number | the number of protons in the neucleus of an atom |
mass number | the sum of the numbers of protons and neutrons in the necleusof an atom |
isotopes | an atom that has the same number of protons as other atoms of the same element but that has a diffrent 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 the mass number 12 |
average atomic mass | the weighted average of the masses of all naturally occuring iscotopes of an element |
metal | an element that is shiny and conducts heat and electricity well |
nonmetal | an element that conducts heat and electricity poorly |
semiconductor | an element or compound that conducts electric current better than an insulator, but not as well as a conductor does |
alkali metal | one of the elements of Group 1 of the periodic table |
alkaline-earth metal | one of the elements of Group 2 of the periodic table |
transition metal | one of the elements of Group 3-12 of the periodic table |
halogen | one of the elements of Group 17 of the periodic table |
noble gas | an unreactive element of Group 18 of the periodic table. |
mole | 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 12g of carbon-12 |
Avogadro's constant | equals 6.02x10(23)/mol; the number of particles in 1 mol |
molar mass | the mass in grams of 1 mol of a substance |
conversion factors | a ratio that is derived from the equality of two different units and that can be used to convert from one unit to another |
valence electron | an electron that is found in the outermost shell of an atom and that determines the atom's chemical properties |