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DCE Chem Unit 2

DCE Chemistry Unit 2 Vocabulary

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
Created by: dcechem



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