CHEMISTRY pp. 31-35

Atoms smallest unit is an atom nucleus: center/core is most of the mass of the atom a. protons: + b. neutrons: 0 electron cloud: outermost level needs to be filled with 8 electrons (or 2 for H) and if not it’s reactive

Atoms: isotopes Atomic number: number of protons Atomic weight (mass): number of protons + neutrons Isotope: different number of neutrons Changes weight Ex: C12 vs C14

Atoms: ions Ion: charged atom due to gaining or losing electrons ( Na vs Na+ )

Element pure substance that can’t be broken into other types of matter each element has its own symbol that uses 1 or 2 letters

Compounds substance made up of 2 or more elements compound behaves different than individual elements EX. Na vs NaCl

held together by bonds a. covalent bonds (strong): 2 or more atoms share electrons b. ionic bonds (weak) : attractions between + and – ions by transferring electrons

Chemical Reactions (rxn) EX. NaOH + HCl  NaCl + H2O reactants: left side products: right side Exergonic/exothermic: release energy like heat, explosion, light etc. – feels warm endergonic/endothermic: requires energy to occur and takes it from the environment- feel cold

Activation Energy energy needed to start a rxn

NEED TO MEMORIZE THE FOLLOWING ELEMENTS AND COMPOUNDS FOR YOUR QUIZ AND TEST! H: hydrogen O: oxygen N: nitrogen C: carbon Na: sodium Cl: chlorine K: potassium S: sulfur COMPOUNDS H2O: water NaCl: sodium chloride/salt H2SO4: sulfuric acid HCl: hydrochloric acid NaOH: sodium hydroxide CO2: carbon dioxide O2: oxygen gas