09 10 15 09 15 15 Chemistry 101 Chapter 2 Proof Electron JJ Thompson Electric charge Magnetic field Beam of particles w the 2 plates differently by the negative and attracted to 1906 Nobel Prize in physics positive Dalton s Theory Elements are made of atoms Atoms are identical Compound simple fraction Does not create destroy Measured mass of e Millikan s experiment Dropping oil e charge 1 60 x 10 19 e mass 9 10 x 10 28 Rutherford Experiment 1908 in chemistry Rutherford Atoms positive charge is concentrated in the nucleus Proton p has opposite charge of electron Mass of p is 1840x mass of e 1 67 x 10 24 g Atom is mostly empty space Atomic radius is 100 pm 10 x 10 10 m Nucleus radius is 5 x 10 3 pm 5 x 10 7 m Atoms are made of subatomic particles Atomic Structure Protons Electrons and Neutrons 3 important ones Unique identity of each element Protons electrically positive Electrons electrically negative Neutrons electrically neutral Small nucleus contains all positive charge and almost all mass Electrons surround the nucleus Occupy most volume Chemical properties depend on electrons Atomic number and Atomic Mass AMU mass of an atom Atomic Number number of protons in nucleus 1 Identifier Average Atomic Mass weighted average of all of the naturally occurring All atoms of a given element have the same number of protons isotopes of the elements On periodic table 09 10 15 09 15 15 Cop per 29 Cu Atomic number Symbol Relative Atomic Mass and the Atomic Mass Standard Carbon 12 Masses of fundamental atomic particles are expressed in atomic mass units u 1 u 1 12 mass of carbon u 1 661 x 10 24 g Mass Number A sum of the number of protons and neutrons A mass number number of protons number of neutrons Gives the isotope Isotopes atoms w the same atomic number but different mass numbers Same number of proton mass difference is due to neutrons Ex hydrogen 1 Protium 2 Deutenum 3 Tritium Percent abundance of atoms of isotope total of isotopes x 100 By mass spectrometry Isotope Abundance Determining Atomic Mass and Isotope Abundance Introduced into spectrometer converted into ions positively charged particles deflected by magnetic field lighter moves more than heavier separated by mass Samples are bombarded w electrons The greater the charge mass ration the more the particle moves Same charge same element Atomic Weight average mass The Periodic Table Atomic weight abundance 100 mass of isotope Features of the periodic table Called groups or families Vertical columns similar chemical and physical properties 1 8 1 2 3 8 main group others are transition metals 2 09 10 15 09 15 15 Good reaction predictor Horizontal rows periods 7 rows Divided into regions Metals Room temp and normal pressure atmospheric are solids can conduct electricity usually ductile and malleable and can form alloys Nonmetals Metalloids Semimetals Some are solids C S P I 10 are gases H O N F Cl H Ne Ar Kr Xe 1 liquid Br Do not conduct electricity Has some physical properties of a metal but chemical Gradually become less metallic as you move left to right Group 1A Alkali metals characteristics of a nonmetal Brief overview Good for salts Reactive w water and halogens Less reactive than 1A Form compounds w analogous formulas Group 2A Alkaline Earth Metals Group 3A metals Group 4A change from nonmetallic metallic behavior Allotropes exist in several different and distinct forms each having its Group 5A N occurs naturally in form of diatomic molecules Group 6A Oxygen Group 7A Halogens own properties Nonmetals Most reactive elements Salts w Alkali metals Group 8A Noble gases Least reactive most stable Transition elements 2A and 3A Metals Have commercial use Rare earth elements Worldwide shortage Lanthanides bottom 2 rows Molecules Compounds and Formulas Molecule smallest identifiable unit which pure substances can be divided 3 Diatomic molecule only 2 atoms Polyatomic 2 Aggregate of 2 in a definite arrangement held together by chemical 09 10 15 09 15 15 forces Formulas Molecular formula describes the composition of molecules What element how many Structural information how atoms are connected and how molecules Condensed Formula indicates how certain atoms are grouped together Structural formulas gives a higher level of structural detail showing how fill spaces all of the atoms are attached within a molecule What how many connectivity Molecular models Empirical formulas shows the simplest whole ratio of the atoms Physical and chemical properties of a molecular compound are related to Ball and stick model spheres of different colors represent the atoms and its structure sticks represent the bonds holding them together Represents 3 D structure their proximity to each other Disadvantage atoms can often be hidden from view Space filling model better representation of relative sizes of atoms and Ionic Compounds Formulas Names and Properties particular level Molecular compounds compounds that consist of discrete molecules at the Ionic compounds formed by combination of positive and negative ions Ions atoms that bear a positive or negative electric charge Metals generally lose one or more electrons Nonmetals frequently gain one or more electrons Monatomic cat ions positively charged ion Cat ions are smaller and loses electrons Group 1A loses 1 1 Group 2A loses 2 2 Group 3A loses 3 3 Charge equal to the group number of the metal Electrons remaining on the cat ion is the same as noble gas that How to predict precedes it Transition metals form cat ions less predictable Monatomic anions negatively charged ion by gaining electrons Ex oxygen grains 2 electrons Observations 4 Nonmetals in group 5A 7A form negative ions having charge equal Electrons is the same as noble gas that follows to group 8 Polyatomic Ion made up of 2 or more atoms w electric charge 09 10 15 09 15 15 Stable together Formulas of Ionic Compounds Salts cat ions anions Electrically neutral no net charge 1 1 ratio of protons and electrons When writing same as empirical the symbol of the cat ion is given first Names of Ions followed by the anion symbol Naming positive ions cat ions Name metal cat ion Charge indicated by roman numeral Monatomic is named by adding ide to the stem Polyatomic are common Anions of halogens are called halide ions Oxyanions containing oxygen Naming negative ions anions nonmetals Greater number of oxygen atoms ate Smaller number of oxygen atoms ite Oxyanions w hydrogen add hydrogen before Properties of Ionic Compounds When particles of opposite charge are near
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