Living organisms are composed of about 25 chemical elementsMost Common ElementsIn the Human Body (96%)Essential Trace ElementsIn the Human Body (0.01%)Trace elements are common additives to food and waterElements can combine to form compoundsAtoms consist of protons, neutrons, and electronsIsotopes• Carbon-12: Protons-6 Neutrons-6 Electrons-6• Carbon-13: Protons-6 Neutrons-7 Electrons-6• Carbon-14: Protons-6 Neutrons-8 Electrons-6Carbon Will Always Have 6 ProtonsOnly The Number Of Neutrons Change in Isotopes!Radioactive isotopes can help or harm usElectron arrangement determines the chemical properties of an atomIonic bonds are attractions between ions of opposite chargeCovalent bonds join atoms into molecules through electron sharingUnequal electron sharing creates polar moleculesHydrogen bonds are weak bonds important in the chemistry of lifePartial Positive EndPartial Negative EndHydrogen bonds make liquid water cohesiveWaters hydrogen bonds moderate temperatureIce is less dense than liquid waterWater is the solvent of lifeThe chemistry of life is sensitive to acidic and basic solutionsAcidic Solutions have A High Concentration of H+ IonsNeutral Solutions have equal concentrations of H+ and OH-IonsBasic Solutions have a low concentration on H+ IonsThe search for extraterrestrial life centers on the search for waterChemical reactions make and break bonds, changing the composition of
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