TOPIC 1 vocabulary
Jan 19, 2016
TOPIC 1
vocabulary
ATOMSmallest part of an element that can enter into a chemical reaction
ATOMIC MASSAverage mass of all the isotopes of a sample of an element
ATOMIC MASS UNIT1/12 the mass of a carbon-12 atom
ATOMIC NUMBERNumber of protons in the nucleus of an atom
COMPOUNDTwo or more elements chemically combined in definite proportion by mass
ELECTRONFundamental particle of matter having a negative charge
ELEMENTSubstance that cannot be broken down or decomposed into a simpler substance by chemical means
EXCITED STATECondition that exists when electrons of an atom occupy higher energy levels, leaving lower energy level(s) vacant
GROUND STATECondition of an atom or ion in which electrons occupy the lowest possible energy levels
HETEROGENEOUSMixture in which substances are not uniformly distributed
HOMOGENEOUSMixture in which substances are uniformly distributed
ISOTOPEAtom of an element with a specific (sometimes unusual) number of neutrons with the protons
MASS NUMBERprotons + neutrons
MIXTURETwo or more substances not chemically combined
NEUTRONParticle in the nucleus of an atom with no charge (neutral)
NUCLEUSDense, positively charged, central core of an atom
ORBITALRegion in an atom (outside the nucleus) where an electron with a specific amount of energy is most likely to be located
PROTONPositively charged particle in the nucleus of an atom
PURE SUBSTANCEMaterial with the same composition throughout; an element or compound
VALENCEOutermost energy level around an atom
WAVE-MECHANICAL MODELCurrent model of the atom in which electrons exist in orbitals of various shapes and pathways, called the electron cloud