Biology 1020-Week 1 Class Notes and Chapter 2 Textnotes-Dr. Sundermann
Biology 1020-Week 1 Class Notes and Chapter 2 Textnotes-Dr. Sundermann Biol 1020 - 001 (BIOL, Christine A. Sunderman, Principles of Biology (1020))
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This 11 page Class Notes was uploaded by Laura Notetaker on Tuesday August 30, 2016. The Class Notes belongs to Biol 1020 - 001 (BIOL, Christine A. Sunderman, Principles of Biology (1020)) at Auburn University taught by Christine A. Sunderman in Winter 2016. Since its upload, it has received 461 views. For similar materials see Principles of Biology 1020-001 in Biology at Auburn University.
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Date Created: 08/30/16
Chapter 2 Textbook Notes for Biology 1020 th All notes taken from Campbell Biology 10 Edition by Campbell and Reese Concept 2.1: Matter consists of chemical elements in pure form and in combinations called compounds Elements and Compounds: o Matter: anything that takes up space and has mass o Element: a substance that cannot be broken down to other substances by chemical reactions o Chemists recognize 92 elements occurring in nature o Compound: a substance consisting of two or more different elements combined in a fixed ratio o A compound has characteristics different from those of its elements The Elements of Life: o Essential elements: only about 2025% of the 92 natural elements are essential for an organism to live a healthy life and reproduce o 96% of living matter is made up of oxygen, carbon, hydrogen, and nitrogen o Trace elements: required by an organism in only minute quantities o Iron (Fe) is needed by all forms of life o The element iodine (I) is an essential ingredient of a hormone produced by the thyroid glands in vertebrates Concept 2.2: An element’s properties depend on the structure of its atoms Subatomic Particles: o Atom: the smallest unit of matter that still retains the properties of an element o There are three subatomic particles that are important in an atom: neutrons, protons, and electrons o Protons and electrons are electrically charged o Each proton contains a positive charge and each electron contains a negative charge o A neutron contains a neutral charge o Atomic nucleus: at the center of an atom and containing tightly packed protons and neutrons o The electrons form a “cloud” of rapidly moving electrons around the nucleus that are negatively charge and that are attracted to the opposite charges of the nucleus. This attraction keeps the electrons circling around the nucleus o Dalton: the measure used for atoms and subatomic particles which is the same as the atomic mass unit or amu of the atom o Neutrons and protons have masses close to 1 dalton/ 1amu o Electrons have a mass of about zero Atomic Number and Atomic Mass: o Atoms of the various elements differ in their number of subatomic particles o All atoms of a particular element have the same number of protons in their nuclei o Atomic number: the number of protons an atom contains; written as a subscript of the element (ex. H) 2 o Mass number: the sum of protons plus neutrons in the nucleus of an atom; written as a subscript of the element o Atomic mass: the total mass of the atom which corresponds to the number of protons and neutrons the atom has because each proton and neutron is equal to 1 dalton/1amu Isotopes: o All atoms of a given element have the same number of protons o However, some atoms have more neutrons than other atoms of the same element and therefore have greater mass o Isotopes: same elements with different atomic forms due to the different number of neutrons o Both C and C are stable isotopes of the element Carbon; this means that their nuclei do not have a tendency to lose subatomic particles o Decay: the tendency for the nuclei to lose subatomic particles o Radioactive isotope: an isotope which the nucleus decays spontaneously fiving off particles and energy Radiometric Dating: o Halflife: the time it takes an isotope for 50% of the parent isotope to decay o Radiometric dating: the ability for scientists to measure the ratio of different isotopes and calculate how many halflives have passed since an organism was fossilized or a rock was formed The Energy Levels of Electrons: o Energy: defined as the capacity to cause change—for instance, by doing work o Potential energy: the energy that matter possesses because of its location or structure o Matter has a natural tendency to move toward the lowest possible state of potential energy o The negatively charged elections are attracted to the positively charged nucleus o The more distant an electron is from the nucleus, the greater its potential energy o Electron shells: the electrons of each separate element are found in different electron shells; each with a characteristic average distance and energy level o First shell: closest to the nucleus and electrons in this shell have the lowest potential energy o Second shell: the second electron shell farther from the nucleus; it has more energy than the first shell o Third shell: farther out from the nucleus and even more energy than the second shell o An electron can move from one shell to another however it must either absorb or lose an amount of energy equal to the difference in potential energy between its position in the old shell and that in the new shell o If an electron absorbs energy, it moves to a shell farther out from the nucleus o If an electron loses energy, it “falls back” to a shell closer to the nucleus Electron Distribution and Chemical Properties: o The chemical behavior of an atom is determined by the distribution of electrons in the atom’s electron shells o The elements are arranged in three rows, or periods, corresponding to the number of electron shells in their atoms o The first shell can hold no more than 2 electrons o The second shell holds a maximum of 8 electrons o The chemical behavior of an atom depends mostly on the number of electrons in its outermost shell o Valence electrons: electrons in the outermost shell o Valence shell: the outermost electron shell o Inert: An atom with a completed valence shell in unreactive which means it will not interact readily with other atoms Electron Orbitals: o Orbital: the space in which an electron spends most of its time; the threedimensional space where an electron is found 90% of the time o The first electron shell has only one spherical s orbital o Second shell has four orbitals: 1 s orbital and three dumbbellshaped p orbitals o No more than 2 electrons can occupy a single orbital o The reactivity of an atom arises form the presence of unpaired electrons in one or more orbitals of its valence shell o Atoms react in a way that completes their valence shells; they use their unpaired electrons to complete their valence shells Concept 2.3: The formation and function of molecules depend on chemical bonding between atoms o The strongest kinds of chemical bonds are covalent bonds and ionic bonds Covalent Bonds: o Covalent bond: the sharing of a pair of valence electrons by two atoms o Molecule: Two or more atoms held together by covalent bonds o Structural formula: where the line represents a single bond which is a pair of shared electrons (ex. H—H) o Double bond: o Each atom that can share valence electrons has a bonding capacity corresponding to the number of covalent bonds the atom can form o Valence: the number of unpaired electrons required to complete the atom’s outermost (valence) shell (ex. Carbon has a valence of 4) o The molecules of H and2 are2pure elements rather than compounds because a compound is a combination of two or more different elements o Electronegativity: the attraction of a particular atom for the electrons of a covalent bond o The more electronegative an atom is, the more strongly it pulls shared electrons toward itself o Nonpolar covalent bond: where a covalent bond is between two atoms and the two atoms equally share the electrons between them; this is because the electrons have the same electronegativity. This usually happens between two atoms of the same element that are covalently bonded o Polar covalent bond: When an atom is bonded to a more electronegative atom and the electrons are not equally shared between the two atoms Ionic Bonds: o Two atoms are so unequal in their attraction for valence electrons that the more electronegative atom strips an electron completely away from its partner o Ions: this causes the atoms to be oppositely charged from each other resulting in them becoming charged therefore known as ions o Cation: a positively charged ion o Anion: a negatively charged ion o Ionic bond: any two ions of opposite charge can form an ionic bond o Ionic Compounds or salts: compounds formed by ionic bonds Weak Chemical Bonds: o Most of the strongest chemical bonds in organisms are covalent bonds which link atoms to form a cell’s molecules Hydrogen Bonds: o Among weak chemical bonds, hydrogen bonds are so central to the chemistry of life that they deserve special attention o Hydrogen bond: the attraction between a hydrogen and an electronegative atom Van de Waals Interactions: o Electrons are not always evenly distributed o The results are everchanging regions of positive and negative charge that enable all atoms and molecules to stick to one another o Van der Waals interactions: individually weak and occur only when atoms and molecules are very close together 2.4 Chemical reactions make and break chemical bonds o Chemical reactions: the making and breaking of chemical bonds leads to changes in the composition of matter o Reactions cannot create or destroy atoms but can only rearrange the electrons among them o Chemical equilibrium: the point at which the reactions offset one another exactly
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