Chapter 2 and Chapter 3
Chapter 2 and Chapter 3 Chemistry 111
C of C
Popular in Chemistry 111
Popular in Chemistry
This 7 page Class Notes was uploaded by Kayla Reece on Tuesday April 26, 2016. The Class Notes belongs to Chemistry 111 at College of Charleston taught by Dr. Forconi in Spring 2016. Since its upload, it has received 15 views. For similar materials see Chemistry 111 in Chemistry at College of Charleston.
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Date Created: 04/26/16
Chapter 2 v an atom is the smallest quantity of matter that still retains the properties of matter v an element is a substance that cannot be broken down in 2 or more substances by any means v concept of atom was proposed by various philiopsers a long time ago v 1808- John Dalton outs forward the atomic theory and the concept that atoms are indivisible v atoms are not indivisible- once a single atom was obtained dividing it into smaller particles Ø the nature, #, and arrangement of subatomic particles determine the properties of atoms, which in turn determine of all things material v subatomic particles and atomic structure Ø in the late 1800s, many scientists were doing research involving radiation, the emission and transmission of energy in the form of waves Ø there commonly used a cathode ray tube, which consists of 2 metal plates sealed inside a glass tube from which most air has been evacuated Ø when metal plates are connecting to a higher voltage such that the negatively charged PARTICLES EMITS INVIVISBLY Ø cathode ray drown to the anode where is passes through a smaller head Ø although invisible the path is revealed when the ray strikes the phosphorus coated surface producing a light v reassure discovered that like charges repeal each other v J.J.thompson discovered electrons Ø His experiment allowed him to determine charge to mass ratio v R.A. Milikan determine the charge of electron by examining the motion of tiny oil drops- - 1.6022 x 10 C 9 v Knowing the charge- to mass ration and change can determine the mass of electrons- 9.10 x -25 10 g v Wilhelm rantgon discovered x-rays emitted by cathode rays hitting a metal plate. They were not deflected by magnetic fields, so they could not consist of charge particles v Antoine Becquerel – discovered radio activity v 2 types of radiation Ø alpha- positively charge particles Ø beta- negatively charge particles Ø Gamma- no charge- neutral v J.J. Thompson- electron exist, atoms are neutral, there must be some positive charge Ø He thought no actual positive particle, but more like a positive diffuse v Ernest Rutherford used a particle to produce the structure of the atom Ø The expected results is that the rays would go straight through the atom because the positive charge was diffused it will not effect ray Ø Results- very rarely got deflected= showing him might be something small and charged concentrated in nucleus v The nucleus accounts for most of the atoms mass and is extremely dense v Protons are positive charge particles in nucleus v Neutrons are neutral- slightly large than protons v All atoms can be i.d. by the # of protons and neutrons they contain v The atomic number is the number of protons in the nucleus v Mass # is the total # of protons and neutrons v Most elements have 2 or more isoto es Ø Have different mass # than ori inal v Isotopes of the same element exhibit similar chemical properties and form some typ s of bonds v The nucleus is a small portion of the total volume o an atom Ø The nucleus contains most m ss Ø Stability in nucleus can relate to density 3 Ø The highest element density is 22.6 / cm v Nuclear stability- is the neutron-to-proto ration Ø Principle factor for nuclear stability is neutron -to proton ratio Ø More w/ even # Ø All w/ atomic # > 83 are radioa tive v Atomic mass is the mass of an atom in the amu unit v The average atomic mass on the periodic table represen ts average mass of the natural occurring mixture of isotop s v Elements are arranged in periods, and ows Ø Group 1 A- alkali me als Ø Group 2A- alkali earth me als Ø Group 6A- Chalogen Ø Group 7A- Halogen Ø Group 8 A- noble gas s Ø Group3b-8b- transition met ls v The moles is defined as the amount of substance that contains many elementary entities as there are atoms in exactly 23 grams of Ca bon Ø 1 mole = 6.022 x 10 ato s Chapter 3 v energy- is the capacity to do work and transfer for heat Ø all forms of energy are either kinetic or potential Ø kinetic energy – is energy of motion § Ek=1/2mu 2 Ø one form of kinetic energy of particular interest to chemists thermal energy § energy associated w/ the random motion of atoms and molecules v forms of energy Ø potential energy is the energy possessed by an object by virtue of its position Ø there are 2 forms § chemical energy-energy stored w/in the structural unit of chemical substances § electrostatic energy- results from the interaction of charged particles v energy can neither be created nor destroyed Ø when energy of one form disappears the same amount of energy reappears in another form of forms § law of conservation of energy v the SI units is the Joule (J) v visible light is only as small component of the continuum of radiant known as the electromagnetic spectrum v properties wave- all forms of electromagnetic radiation though the waves Ø waves can be characterized by § wavelength- the distance between identical points on successive waves § frequency- the # of waves that mass through a particular point in 1 sec § amplitude0 the vertical distance from the midline of a wave to the top of the peak or the bottom of the trough v the nature of light Ø the speed of light ( c) through a vacuum is a constant § c=3.00 x 10 m/s § C= λv v The electromagnetic spectrum Ø One electromagnetic wave has both an electric field component § The electric and magnetic components have the same frequency and wavelength v The double slit experiment (Maxwell, 1873) Ø When light passed though 2 closely spaced slits an interference patterns are produced Ø Constructive interference is a result of adding waves that are interphase Ø Destructive interference is a result of adding wave structure that are at phase v This type of interference is typical of waves and demonstrates that wave and nature of light v Quantum theory Ø When a solid is heated it emits electromagnetic radiation, known as black body radiation, are actual range of wavelengths Ø Classical physics failed to completely explain the phenomenon Ø Assumed that radiant energy was continuous; that is it could be emitted or absorbed in any amount v Max Planck suggested that radiant energy is only emitted or absorbed in discrete quantities, like small packages of bundles Ø A quantum of energy is small quantity of energy that can be emitted or absorbed v The energy E of a single quantum of energy is E= hv (h= Planks constants) v Bohrs’s theory of hydrogen atom- the emission spectrum of both sunlight and a heated solid are continuous, all wavelengths of visible light are present v Atom line spectra- are the emission of light only at specific wavelengths Ø Every element in a gas phase has its own unique emission spectrum v The Rydberg equation (empirical) can be used to calculate the wavelengths of 4 visible lines in the emission spectrum of hydrogen v In 1913 Neils Bohr attributed the emission of radiantly and energized hydrogen atom to the electron dropping from high energy orbital to a lower one Ø As electron dropped it gave up a quantum of energy in the form of light Ø Bohr showed that the energies of electron in a hydrogen atom are given by the equation § E = 2.18x10 (1/n ) 2 n Ø Energy means attraction between nucleus and electron v As electron gets closer to the nucleus, n decreases Ø E =n2.18x10 (1/n ) 2 Ø E becomes larger in absolute value (but more negative) as n gets smaller n Ø E ns more negative when n=1 § Called the ground state, the lowest hierarchy stated of atom § For H- this is stable v The stability of electron decreases as n increases v Each energy state in which n>1 is called excited state v Bohr’s theory explains the line spectrum of H atom v Radiant energy absorbed by the atom causes the electron to move rom ground state n=1 to and excited state n>1 v Conversely, radiant energy is emitted when the electrons movers from high energy state to a lower energy state v Quantized movement of the electron from one energy state to another is analogous to a ball moving and down steps v Suppose an electron is initially in an excited state (n ) 1uring emission the electron droms to a lower energy lever (n )f v The energy difference is E=hv=-2.18x10 ((1/n ) -(1/nf ) i2 v Wave properties of matter Ø Louis de Broglie reasoned that if light can behave a stream of particles (photon), then electrons could exhibit wave like properties Ø According to de Broglie, electrons behave like standing waves Ø Only certain wavelengths are allowed Ø At a node, the amplitude of the wave is zero Ø De Broglie wave -λ=n/mu v Bohr’s theory explained the behavior of the hydrogen atom but did not explain those v The Heisenberg uncertainty principle state that it is impossible to know simultaneously both the momentum and the position of x of a particle w/ uncertainty v Quantum mechanics Ø Erwin schroclinger derived a complex mathematical equation formal to incorporate the wave on a particles electron 2 Ø The probability of finding an electron in a certain area of space is proportional to Ψ and is called electron density v The schrodinger equation specifics possible energy states on electron can occupy in a hydrogen atom v The energy states were functions are characterized by a set of quantum # v Instead of referring to orbitals in bohr v Quantum # are required to describe the distribution of electron density in an atom v There are 3 qunatum numbers necessary to describe atomic orbitals Ø The principle quantum number (n)- size Ø The angular movement quantum number (l)- shape Ø The magnetic quantum number (m) specificlorientation v The principle quantum number (n) designates the size of the orbital Ø Lage values of n corresponds to larger orbitals Ø The allowed values f n are itnergral #s 1,2,3 …… Ø The value of n corresponds to the value of n in bohrs model Ø A collection of orbitals w/ the same value of n is called a shell v Quantum #- angular(l) describes shape Ø The value of 1are intergers that depend on the value of the principal quantum number Ø The allowed values of l range from o to n-1 v Magnetic quantum number (m) depenls on l Ø N=2, l=0,1-m =0 or m =-1,0,+1 Ø Desribces orientation of oribatl space Ø A beam of atom is split by magnetic field § Statistical , half of electrons spin clockwise, other one spins counter v Shinning light onto a metal surface can be thought of as shooting a beam of particles- photon- at metallens Ø If v of the photon equals the energy that binds the electrons in metal, then height will have enough energy to knock the electron loose Ø If we use light of angular v, then not only will the electrons be knocked loose, but they will also acquire some kinetic energy § Hv= KE+w v S orbitals- 2 s 1s<2s<3s Ø Spherical is half but different in size v The p orbitals-90 to one another v v d orbitals v v the enrgy gives the orbitals in the H2 atom depending on the principle quantum number Ø f=z orbitals v the electron configuration describes how the electrons are distributed on various atomic oribitals 1 Ø h ground state hydrogen atom, the electron is found in 1 s orbital – 1s Ø ground state is the most stable state of th configuration v if the hydrogens electron is found in a higer energy orbital that atom is excited v the helium emissions are more complex than the hydrogen spectrum Ø each orbital can only hold 2 electrons Ø ground state of helium = 1s 2 v the 2s, 2 p etc- are no longer on the same energy level v according to the Pavie exclusion principle, no 2 electrons in an atom can have the same 4 qunatum # Ø one has to have m of s /2 or -1/2 v the aufbau principle states that electrons are added to the lowest energy orbitals first before moving higher energy orbitals v hunds rule- the most stable arrangement of electrons is that are in which the # of electrons w/ the same spin is maximized v when there are 1 or more unpaired electrons, as in the case of O and2of atoms paramagnetic v general rules Ø electron reside in the available orbitals of the lowest possible energy Ø each orbital can accommodate a max of 2 electrons Ø electrons will not pair in degenerate orbitals of an empty orbital is lined up v 57 there is a a gap-lanthanide (rare earth) snse v transition maetals 3b-8b and 1 b are the transition metals v there are not able exceptions to the transion 1 5 1 10 Ø chronimum- [Ar]4s 3d or copper [Ar] 4s 3d
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