chemicalfoundations - Chemical Foundations for Cells for...

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Unformatted text preview: Chemical Foundations for Cells for Chapter 4 Most Common Elements in Living Organisms Living Oxygen Hydrogen Carbon Nitrogen However trace elements However are very important are Atoms Atoms Have Energy Energy Energy the ability to do work the energy in atoms the comes from various sources; collectively described as chemical energy energy Atoms What Makes Up an Atom? Atom Nucleus contains protons and neutrons Protons positively charged Neutrons no charge Electrons negatively charged; move in regions outside of negatively outside the nucleus the Atomic Structure Generalized Structure of an Atom Generalized nucleus electron HYDROGEN proton Atoms Atoms Make Elements Atoms Atom smallest particle of an element that retains the characteristics of that element element ex. carbon atoms in a diamond give ex. the diamond its hardness and light refracting properties refracting all elements are made of atoms Elements Elements Make Matter Elements Matter anything that has mass and takes up space Element a substance that cannot be broken down into substance simpler substances simpler Periodic Table Periodic Table Periodic chart created to demonstrate the periodic chemical chart and physical properties of the elements. and 6 c Carbon 12.0111 Atomic Number: shows the number of electrons or protons in an atom of the element Element Symbol Element Name Atomic Mass: shows the relative mass of the atom as compared to a standard mass The Periodic Table Compounds Compounds from Elements Compounds Compounds substances substances made from elements that are made combined chemically combined elements combine to form billions of different elements billions substances with new properties new Compounds Chemical Formula Chemical shows shows the kinds and proportions of atoms atoms in a compound in Substance Water Chemical Formula H2O 2 atoms of Hydrogen 1 atom of Oxygen Compounds Molecules Molecules the the smallest units of a compound that still have the properties of that compound compound O O H H H H Ions Ions Ions electrically charged atoms or groups of atoms a substance like table salt (NaCl) is made substance from electrically charged particles electrically Remember: Opposites attract! Kinky! Ions Ions Can Be Groups of Atoms Ions Ion* CH3COO- (acetate ion) (acetate OH - (hydroxide ion) OH Charge -1 -1 *there is a net charge on the entire group of atoms Ionic Bonding Negatively Charged Ions Negatively for for example: a chlorine atom has 17 protons and 17 electrons (thus, it is neutral) 17 if a chlorine atom gains one electron, it has 18 if gains it electrons and 17 protons for a net electrons -1 charge Chlorine Atom Ion 17p+ 17p+ 17e­ 18e­ 0 charge ­1 charge Cl ­ Ionic Bonding Positively Charged Ions Positively sodium has 11 protons and 11 electrons sodium loses electrons when it forms sodium loses compounds compounds a sodium ion has 10 electrons & 11 protons Sodium Atom Ion 11p+ 11p+ 11e­ 10e­ 0 charge +1 charge Na + What Determines Whether Atoms Will Interact? Atoms The number and arrangement of their The valence electrons valence Electrons Electrons Carry a negative charge Repel one another Repel Are attracted to protons in Are the nucleus the Move in orbital's Move volumes of space that surround the nucleus surround y Z X When all p orbitals are full Electron Orbitals Electron Orbitals Orbitals can hold up to two electrons electrons Atoms differ in the number of Atoms occupied orbitals occupied Orbitals closest to nucleus are Orbitals lower energy and are filled first lower Shell Model Shell First First shell Lowest energy Holds Holds 1 orbital with up to 2 electrons electrons Second 4 shell orbitals hold up to 8 orbitals electrons electrons CALCIUM 20p+ , 20e- Electron Vacancies Electron Unfilled Unfilled shells make atoms likely to react atoms Hydrogen, carbon, Hydrogen, oxygen, and nitrogen all have vacancies in their outer shells outer CARBON 6p+ , 6e- NITROGEN 7p+ , 7e- HYDROGEN 1p+ , 1e- Types of Bonding Types of Bonding Types Ionic Bonds Covalent Bonds Hydrogen Bonds Ionic Bonding Ionic Bond Ionic attraction between oppositely charged ions attraction oppositely the negative chloride ion (Cl-) and the positive the negative sodium ion (Na+) are attracted to each other sodium are forms when an atom such as sodium loses an loses electron to another atom that accepts electrons, electron such as chlorine such Ions in Our Bodies What Role Do Ions Play in Our Bodies? What the transfer of electrons and the formation of ions are the essential to living organisms essential part of the photosynthesis process involves electron part photosynthesis transport reactions transport your nerve and muscle cells cannot function without your nerve the proper amounts of sodium, potassium and calcium ions calcium Covalent Bonding Covalent Bonding Covalent results when two atoms share a pair of electrons electrons the shared electrons provide the “glue” that the holds the atoms together holds Covalent Bonding Single Bonds Single The electrons shared between hydrogen and oxygen atoms in water can be shown by straight lines to represent the covalent bonds Each bond represents two shared electrons Each two O H H H2O this line represents one shared pair of electrons Covalent Bonding Double Bonds Double The The carbon dioxide molecule consists of two double bonds to the oxygen atoms. O this line represents two shared pairs of electrons C CO2 O Chemical Reactions Chemical Reactions Chemical the the process by which elements react to form new compounds new involves the rearrangement of chemical bonds involves with a release or absorption of energy with 6CO2 + 6H2O + Energy reactants reactants C6H12O6 + 6O2 products Chemical Reactions Reading a Chemical Equation Reading 6CO2 + 6H2O + Energy 6H reactants reactants this this C6H12O6 + 6O2 6O products equation represents 6 molecules of carbon dioxide and six molecules of water plus energy reaction to give one molecule of sugar( C6H12O6) sugar( and six molecules of oxygen six Nonpolar Covalent Bonds Nonpolar Atoms share electrons equally Nuclei Nuclei of atoms have same number of protons number Example: Hydrogen gas (H-H) Polar Covalent Bonds Polar Number Number of protons in nuclei of participating atoms is NOT equal participating Electrons Electrons spend more time near nucleus with most protons nucleus Water Water - Electrons more attracted to O nucleus than to H nuclei nucleus Hydrogen Bonding Hydrogen Other Other molecules can polar covalently molecule can bond to another. molecule Atom Atom in one polar covalent molecule can be attracted to oppositely charged atom in another such molecule another H+ + + _ O H H+ + _ O H + Examples of Hydrogen Bonds one large molecule another large molecule a large molecule twisted back on itself Fig. 2.12, p. 27 Chemical Reactions Energy in Reactions Energy Exothermic reactions the breaking of bonds absorbs less energy the than is released in forming new bonds than Endothermic reactions the breaking of bonds absorbs more energy the than is released during the formation of new bonds bonds Isotopes Isotopes Atoms Atoms of an element with different numbers of neutrons (different mass numbers) numbers) Carbon 12 has 6 protons, 6 neutrons Carbon 14 has 6 protons, 8 neutrons Radioisotopes Radioisotopes Have Have an unstable nucleus that emits energy and particles and Radioactive decay transforms radioisotope Radioactive into a different element into Decay occurs at a fixed rate Radioisotopes as Tracers Radioisotopes Tracer Tracer is substance with a radioisotope attached to it radioisotope Emissions from the tracer can be Emissions detected with special devices Following movement of tracers is Following useful in many areas of biology useful Thyroid Scan Thyroid Measures Measures health of thyroid by detecting radioactive iodine taken up by thyroid gland gland normal thyroid enlarged cancerous Other Uses of Radioisotopes Other Drive artificial pacemakers Radiation therapy Emissions from some radioisotopes can Emissions destroy cells. Some radioisotopes are used to kill small cancers. kill ...
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This note was uploaded on 10/12/2011 for the course BIO 101 taught by Professor Martin during the Spring '08 term at Rutgers.

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