General Chemistry Week Two Notes
General Chemistry Week Two Notes CHEM103090
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This 8 page Class Notes was uploaded by Nina Drachman on Saturday September 19, 2015. The Class Notes belongs to CHEM103090 at University of Delaware taught by Graves PhD,Kimberly Susan in Fall 2015. Since its upload, it has received 57 views. For similar materials see General Chemistry in Health and Human Services at University of Delaware.
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Date Created: 09/19/15
Chemistry Lecture Sep 8 Chapter 2 Atoms Molecules and Ions Oxygen atoms for PET scans PET scan positron emission tomography uses emission from safely radioactive compounds to get internal images in the body The radioactive component of many common imaging agent can be made from water Why is it so dif cult The Atom 1 What are the parts of the atom 2 What characteristics of an atom distinguish elements 3 Why are some forms of an element different from others Dalton s Atomic Theory 1 All matter consists of atoms tiny indivisible particles of an element that cannot be created or destroyed 2 Atoms of one element cannot be subdivided created or destroyed during chemicals reactionsDWRONG 3 Atoms of an element are identical in mass and other properties and are different from the atoms of any other element 4 Comounds result from the chemical combination of a speci c ratio of atoms of different elements Atomic Structure Electrons 1 Thompson 0 Ray bends in magnetic eldray consists of charged particles 0 Ray bends toward positive plate in electric eldrays consist of negative particles 0 Ray is identical for any cathodeljthese particles are found in all matter Thompson39s Model of the Atom 0 Plumpudding model E distributed throughout diffuse pos charged squishy sphere Rutherford39s Experiment 0 Bombard a thin gold foil with pos charged particles to test Thompson s model of the atom 0 He expected the beam to go through 0 But a small amount of the particles bounced back dramatically o The positive charge in the atom is concentrated in the middle that s what they must have hit 0 Conclusion the nucleus The Nuclear Atom The nucleus o Is the pos charged center of an atom containing nearly all of the atom s mass 0 Consists of 2 types of particles Protons pos charged subatomic particles Neutrons electrically neutral subatomic particles Modern Day View of Atoms Cloud of electron density Nucleus o Protons o Neutrons 0 Also called nucleons 0 Elements are differentiated by the number of protons in the nucleus Atomic numberprotons Mass numberprotons neutrons Removing neutronisotope same element but different mass Symbols with Mass and Atomic Number Element symbol one of two letter symbol to indentify the type of atom Atomic mass total number of nucleons in the nucleus Atomic number number of protons in the nucleus determines the identity of the element and is the number on the periodic table Atomic Mass Units Atomic mass units amu 0 Unit used to express the relative masses of atoms and subatomic particles 0 1 protons is about 1 amu 1 neutron is about 1 amu 1 electron is too small to count 0 6 protons 6 neutrons 12 amu for a carbon atom Isotopes Isotopes o Atoms of an elements containing the same number of protons but different number of neutrons Occur in difference amounts depending on the element 0 Natural abundance proportion of a particular isotope usually expressed as a percentage relative to all the isotopes for that element in a natural sample 0 Some isotopes are not stable and decay radioactively Average Atomic Mass Scientists and engineers typically deal with large numbers of atoms ex gramquantities Usually this means all isotopes of an atom are present in a sample in their relative s Periodic table therefore re ects the weighted average atomic mass of an elements Weighted average atomic mass of neon 0 199924 x 0904838 2099395 x 0002696 219914 x 0092465 201797 amu 0 Adding the three isotopes times the natural abundance as a decimal Why is it so dif cult to get oxygen 18 the average is about 16 Chem Lecture Sep 10 Chapter 2 Atoms Molecules Ions Focus Question Carbon dioxide is a very important molecule in our respiration cycle and generally isn t dangerous Breathing in cardon monoxide is usually fatal leading to the nickname quotThe Silent Killerquot What do these names tell us about the difference between these two compounds Introduction to Ions Changing the number of electrons leads to a charge Just like changing the number of neutrons leads to an isotope Na 11 protons 11 electron no charge Na 11 protons 10 electrons l 1 charge 0 Losing an electron forms a cation positive charge 0 Metals form cations 0 Same element same mass different charge 0 Now an ion 0 8 protons 8 electrons no charge 02 8 protons 10 electrons l 2 charge 0 Gaining an electron forms an anion negative charge 0 Nonmetals form anions 0 Same element same mass different charge 0 Now an ion Ionic Compounds Ionic compounds 0 Consist of charged particles ions formed by transfer of electrons between atoms 0 Ions held together by electrostatic forces 0 When atoms become ions they can become compounds because they attract each other Cations ions formed with positive charge formed by meta5 Anions ions with negative charge formed by non meta5 Mendeleev s Periodic Table Ordered elements by atomic mass now organized by atomic number Arranged elements in columns based on similar chemical and physical properties Left open spaces in the table for elements not yet discovered he realized there were elements we didn t know about Current Periodic Table Organization Now organized by atomic number number of protons Z 0 Equal to number of electrons in neutral atoms 0 Why aren t the numbers in order Most of periodic table are meta5 they lose electrons Nonmetals on the complete right gain electrons Metalloids in between metals and nonmetals 0 Some cases they act like metals some cases they act like nonmetals Summary of Ion Charges Atoms with gainlose electrons to be stable like noble gases D able to predict charge of ion formed from an element based on element s position on periodic table Every element wants to be like noble gases column 18 Column 1 1 Column 2 2 Column 12 3 Column 14 2 or 4 Column 15 3 Column 16 2 Column 17 1 Column 18 O noble gases Transition metals have different charges middle part of PT Formula Units Formula unit Smallest electrically neutral unit of an ionic compound Naming Binary Ionic Compounds Binary ionic compounds consist of cations usually metals 0 Ex MgC2 o Cation named rst using name of element Mg magnesium o Anion named by adding the ide suf x to the name of the element Cl chlorine chloride 0 Formulas for ionic compounds must always be neutral Mg2 Cl x 2 Binary Ionic Compounds with different charges For metals that form cations with different charges a roman numeral is added to indicate the charge of the cation FeCl2 Fe2 o lronll chloride FeCI3 l Fe3 o lronlll chloride Molecular Compounds Molecular compounds 0 Composed of atoms held together in molecules by covalent bonds Covalent bonds 0 Bonds between two atoms created by sharing one of more pairs of electrons Molecular compounds are composed of nonmetas Hydrogennonmetal Naming Molecules Binary molecular compounds ex SO3 exactly two nonmetal elements 0 First element in the formula is named rst S sulfer 0 Second element name is changed by adding suf x ide O oxygen loxide 0 Add pre xes to indetify quantity of atoms SO3 sulfur trioxide Rules for Using Pre xes 1 Do not use the pre x mono when naming the rst element only when naming the second element 2 Pre xes ending with 0 or a are modi ed when used with elements beginning with vowels a Ex P4010 tetraphosphorus decaoxide Polyatomic lons Polyatomic ions charged chemical ion 0 Charged group of two or more atoms joined together by covalent bonds Oxoanions o Polyatomic anions containing oxygen in combination with one or more other elements 0 Ex nitrate NO3 GOING TO NEED TO MEMOMRIZE POLYATOMIC IONS Metal nonmetal bond ionic Pre xes ONLY for molecular compounds covalent Focus question its unstable One less oxygen
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