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DCE Chem Unit 2
DCE Chemistry Unit 2 Vocabulary
| Term | Definition |
|---|---|
| chemical symbol | a one or two letter representation of an element |
| law of conservation of mass | in any physical change or chemical reaction, mass is conserved; mass can be neither created nor destroyed |
| atomic mass | the number of protons plus the number of neutrons |
| atomic number | the number of protons in an element |
| proton | the positive part of the atom, found in the nucleus |
| neutron | the neutral part of the atom, found in the nucleus |
| electron | the negative part of the atom, found outside the nucleus |
| isotopes | different varieties of an element that vary only in the number of neutrons |
| nucleus | the area in the center of the atom, contains protons and neutrons |
| radioactivity | the process by which the nucleus of an atom changes |
| alpha particle | essentially a helium nucleus emitted during radioactive decay, atomic number of 2 and mass of 4 |
| emission spectrum | a pattern formed when light passes through a prism or diffraction grating to separate it into the different frequencies of light it contains |
| Aufbau principle | the rule that electrons occupy the orbitals of lowest energy first |
| Hund's rule | electrons occupy separate orbitals of the same energy before they double up |
| Pauli exclusion principle | an atomic orbital may describe at most two electrons, each with opposite spin |
| electron configuration | a way of showing where the electrons in an atom are, like an address |
| orbital notation | a way of showing where the electrons in an atom are, using arrows to represent the electrons |
| electron dot diagram | a notation that shows the valence electrons of an atom around the chemical symbol for that element |
| valence electrons | electrons in the outermost energy level of an atom |
| ground state | the lowest possible energy level of an electron |
| excited state | when an electron has been given energy and has temporarily moved to a higher energy level |
| atom | the smallest part of an element that retains its identity in a chemical reaction |
| ion | an atom that has lost or gained one or more electrons |
| half-life | the time required for half of a radioactive substance to decay |
| strong nuclear force | a force of attraction which helps hold the nucleus together |
| beta | an electron that is formed from the breakup of a neutron during a nuclear reaction |
| gamma | a type of energy that can be emitted during a nuclear reaction |
| positron | a particle with the mass of an electron but with a positive charge that is emitted during a nuclear reaction |
| electron capture | a type of nuclear reaction in which an inner electron is captured by the nucleus, resulting in the formation of a different element |
| fission | when a large, unstable nucleus breaks apart |
| fusion | the joining together of two nuclei to produce a larger nucleus |
| plum pudding model | a model of the atom in which the negative electrons are dispersed throughout a positive atom, like plums in pudding |
| gold foil experiment | an experiment that revealed that the nucleus is small and has a positive charge |
| cathode ray tube experiment | an experiment that revealed that all atoms have electrons and that electrons are negative |
| law of definite proportions | in samples of a compound the masses of elements are always in the same proportions |
| law of multiple proportions | when two elements form more than one compound, the masses of one element compared to the other are always small, whole numbers |
| chemical reaction | a reaction in which chemical bonds are broken and new bonds are formed |
| nuclear reaction | a reaction involving the nucleus of an atom, whereby one atom can be transformed into a different element or isotope |
| electrostatic force | The attraction or repulsion of particles or objects because of their electric charge (opposite charges attract, like charges repel) |
| strong nuclear force | the force that binds protons and neutrons together to form the nucleus of an atom |
| mass defect | the difference between the sum of the masses of the individual protons and neutrons and the mass of the whole atom |
| binding energy | the energy that is lost when a nucleus is created from protons and neutrons |
| electromagnetic spectrum | the complete range of the wavelengths of electromagnetic radiation, beginning with the longest radio waves and extending through visible light all the way to the extremely short gamma rays |
| spectroscopy | the measurement of the absorption or emission of electromagnetic radiation by atoms or molecules |
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