Chapter 2 NotesSection 2.1Atoms: The smallest unit of a chemical elementNUCLEUS: The centrally located positive part of an atom containing the protons and neutronsELECTRONS: The negative particles that surround the nucleusPROTONS: The positive charged subatomic particle in a nucleusNEUTRONS: A particle of matter with no electrical charge that makes up part of the nucleusMASS: A measure of the quantity of matter present Dalton=standard unit of measurement used to measure the mass of a particle1 dalton (Da)=1.7 x 10^-24 gramsELEMENT: A pure substance that contains only one kind of atomATOMIC NUMBER: The number of protons an atom containsMASS NUMBER: The total number of protons and neutrons in an atom’s nucleusISOTOPE: A chemical that has the same number of protons, but differ in number of neutronsATOMIC WEIGHT(ATOMIC MASS): The average mass number of a sample of atom’s from a given elementRADIOISOTOPE: A radioactive isotope of an element that is unstable and spontaneously gives off energy in the form of alpha, beta, or gamma radiation from the nucleusMOLECULES: A chemical substance made up of two or more atoms joined by covalent bonds or ionic attractionsORBITAL: A region in space surrounding the atomic nucleus in which an election is most likely to be foundELECTRON SHELLS(ENERGY LEVELS): The region surrounding the atomic nucleus at a fixed energy level in which electrons orbitValance shell=outermost shell-Reactive atoms can attain stability either by sharing electrons with other atoms or by losing or gaining one or more electrons——————————————————————————————————————————————————————————————————Section 2.2CHEMICAL BOND: An attractive force that links two atoms together in a moleculeCOVALENT BOND: Forms when two atoms attain stable electron numbers in their outermost shells by sharing one or more pairs of electronsCOMPOUND: A pure substance made up of two or more different elements bonded together in a fixed ratioMOLECULAR WEIGHT(RELATIVE MOLECULAR MASS): The sum of the atomic weights of all atoms in a molecule-covalent bonds are VERY strongELECTRONEGATIVITY: The attraction force that an atomic nucleus exerts on electrons in a covalent bond-depends on how many + charges and the distance b/w the nucleus and electrons in valence shellNONPOLAR COVALENT BOND: The bond formed when two atoms that are close together in electronegativity share electrons equallyPOLAR COVALENT BOND: A bond in which the electrons are drawn to one nucleus more than the other, resulting in an unequal distribution of chargePOLAR: A molecule with separate and opposite electric charges at two ends, or polesION: An electrically charged particle that forms when an atom gains or loses one or more electronsCATION: A positively charged ionANION: A negatively charged ionCOMPLEX IONS: Groups of covalently bonded atoms that carry an electric chargeIONIC ATTRACTIONS: Bonds formed as a result of the electrical attraction between ions bearing opposite chargesHYDROGEN BOND: A weak bond formed by the attraction of a slight positive charged hydrogen atom and a slightly negative charged oxygen/nitrogen atomHYDROPHILIC: water-lovingHYDROPHOBIC: water-hatingHYDROCARBON MOLECULES: A compound containing only carbon and hydrogen atomsVAN DER WAALS FORCES: Very weak attractions between atoms resulting from the interaction of the electrons of one atom with the nucleus of another————————————————————————————————————————————————————————————————————Section 2.3CHEMICAL REACTION: Occurs when moving atoms collide with sufficient energy to combine or to change their bonding partnersREACTANT: A chemical substance that enters into a chemical reaction with another substancePRODUCT: The molecule that results from the completion of a chemical reactionENERGY: The capacity to do work, or the capacity for change————————————————————————————————————————————————————————————————————Section 2.4SPECIFIC HEAT: The amount of heat energy required to raise the temperature of 1 gram of a substance by 1 degree CelsiusHEAT OF VAPORIZATION: The energy that must be supplied to convert a molecule from a liquid to a gas at its boiling pointCOHESION: The capacity of water molecules to resist coming apart from one another when placed under tensionSOLUTION: A liquid and its dissolved solutesSOLUTE: A substance that is dissolved in a liquid to form a solutionSOLVENT: The liquid in which a substance is dissolved to form a solutionMOLE: The amount of a substance numerically equal to the molecular weightAVOGADRO’S NUMBER: The constant number of molecules in a moleACID: Substances that release H+BASE: Substances that accept H+BUFFER: A mixture of a weak acid and its corresponding base, or a weak base and its corresponding