Tortora - Chapter 2 - The Chemical Level of Organization.ppt

Tortora - Chapter 2 - The Chemical Level of...

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Unformatted text preview: 2-1Chapter 2 The Chemical Level of OrganizationMatterelementsatoms and moleculesChemical bondsChemical energyChemical reactionsInorganic compoundsOrganic compounds2-2How Matter is OrganizedChemistry is the science of the structure and interactions of matter.all living things consist of matter.Matter is anything that occupies space.mass is the amount of matter in any object.weight is the force of gravity acting on matter.In outer space, weight is close to zero, but mass remains the same as on Earth.2-3Chemical ElementsElements are substances that can not be split into simpler substances by ordinary means.112 elements ( 92 occur naturally )26 of naturally occurring elements are in the bodyrepresented by chemical symbols ( first 1-2 letters of name )4 elements form 96 % of the bodys masshydrogen, oxygen, carbon and nitrogenTrace elements are present in tiny amounts such as copper, tin, selenium & zinc2-4Structure of AtomsAtoms are the smallest units of matter that retain the properties of an elementAtoms consist of 3 types of subatomic particlesprotons, neutrons and electronsNucleus contains protons (p+) & neutrons (neutral charge)Electrons (e-) surround the nucleus as a cloud (electron shells are designated regions of the cloud)2-5Electron ShellsMost likely region of the electroncloud in which to find electrons Each electron shell can hold onlya limited number of electronsfirst shell can hold only 2 electrons2nd shell can hold 8 electrons3rd shell can hold 18 electronshigher shells (up to 7) hold many more electronsNumber of electrons = number of protonsEach atom is electrically neutral; charge = 02-6Atomic Number & Mass NumberAtomic number is number of protons in the nucleus. .Mass number is the sum of its protons and neutrons.2-7IsotopesAtoms of an element with different numbers of neutrons & different mass numbers All isotopes of an element have same propertieshave same number of electrons (which determine its chemical properties)Only radioactive isotopes are unstabledecay over time to a more stable configurationhalf-life is time required for half of the radioactive atoms in a sample to decay2-8Effects of RadiationRadioactive isotopes can pose a serious health threatbreak apart molecules & cause tissue damageDecay of naturally occurring radioactive isotopes releases small amounts of radiationradon-222 gas may seep out of soil in basementincreases the risk of lung cancerRadioactive isotopes used beneficially in medical imaging procedures & treat cancer2-9Atomic MassMass is measured as dalton (atomic mass unit)neutron has mass of 1.008 daltonsproton has mass of 1.007 daltonselectron has mass of 0.0005 daltonAtomic mass (atomic weight) is close to the mass number of its most abundant isotope.2-10Ions, Molecules, & CompoundsIons are formed by ionizationan atom that gave up or gained an electron...
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This note was uploaded on 06/11/2009 for the course BIOL 251 taught by Professor Hurrell during the Spring '09 term at Delgado CC.

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Tortora - Chapter 2 - The Chemical Level of...

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