Flashcards › Chp 17 vocab Mrs. Strong

substance that cannot be broken down into simpler substances element negatively charged particle that exists in an electron cloud formation around an atom's nucleus electron positively charged particle in the nucleus of an atom proton elictrically neutral particle that has the same mass as a proton and is found in an atom's nucleus neutron region surround the nucleus of an atom, where electrons are most likely to be found electron cloud number of protons in the nucleus of an atom of a given element atomic number atoms of the same element that have different numbers of neutrons isotope the sum of neutrons and protons in the nucleus of an atom mass number release of nuclear particles and energy from unstable atomic nuclei radioactive decay the changing of one element into another through radioactive decay transmutation time needed for one-half of the mass of a sample of a radioactive isotope to decay half-life