BIOS 208 1st Edition Lecture 4 Outline of Last Lecture I. Chemical Basis of LifeII. Definition of an ElementIII. Chemical CompoundIV. Elements essential to lifeV. Trace ElementsVI. Nitrogen DeficiencyVII. Where are elements found?VIII. Atomic StructureOutline of Current Lecture I. IsotopesII. Atomic Number and Atomic MassIII. Isotopes of CarbonIV. Hydrogen IsotopesV. Unstable Radioactive IsotopesCurrent LectureI. IsotopesA. Isotopes occur when forms of elements have the same chemical properties, but differentmass.B. In nature, elements occur as mixtures of isotopes.C. All isotopes have the same number of protons (same atomic number), but different numbers of neutrons, therefore, they have different atomic weights.D. For Carbona)12C atomic weight 6C atomic number.b)12C, 13C and 14C all have 6P, so all are carbon.II. Atomic Number and Atomic MassA. Atomic number = number of protons in nucleus.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a) H = 1 Proton (P).b) C = 6 P.c) U= 92 P.B. If there are the same no. of electrons in orbitals around the nucleus, the overall charge isneutral.C. Atomic mass = no. of protons + no. of neutrons.D. For Calciuma) Atomic mass is 40.b) Atomic number is 20.E. Thus, no. of neutrons = atomic mass – atomic no. (20).F. For potassiuma) Atomic mass is 39.b) Atomic number is 19.G. So the no. of neutrons is also 20…the same as for Ca.H. Properties of elements are indirectly determined by the no. of protons.I. This is because the number of protons is equaled by the number of electrons in the atom.J. The number of electrons determines the chemical properties of each element.III. Isotopes of Carbon*All are carbon, and behave chemically like carbon*PROTONS NEUTRONS ELECTRONS ABUNDANCE12C, 6C 6 6 6 99%13C,6C 6 7 6 1%14C,6C 6 8 6 Tiny%IV. Hydrogen IsotopesHydrogen 1P 0N 1EDeuterium 1P 1N 1ETritium 1P 2N 1EV. Unstable Radioactive IsotopesA.14C is an example of an unstable isotope which decays and fragments at a known rate.B. Radioactive emission of particles from the nucleus occurs.C.14C emits beta-particles, which are smaller particles plus energy.D. Decay of any isotope occurs at a characteristic rate which is described as its half-life (t 1/2).E.14C: 5730 years.F.32P: 14 days.G.238U:4.5billion
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