Download ATOMIC STRUCTURE

Copyright Sautter 2003
ATOMIC STRUCTURE
QUANTUM THEORY
&
ELECTRONIC CONFIGURATION
OF ATOMS
SUBATOMIC STRUCTURE
• ALL ATOMS CONSIST OF PROTONS, NEUTRONS
AND ELECTRONS
• PROTONS ARE POSITIVELY CHARGED PARTICLES
THAT RESIDE IN THE NUCLEUS AT THE CENTER
OF THE ATOM
• NEUTRONS ARE PARTICLES WITH NO CHARGE
THAT ALSO ARE CONTAINED IN THE NUCLEUS.
• ELECTRONS ARE NEGATIVELY CHARGED
PARTICLES THAT ARE EXTERNAL TO THE
NUCLEUS.
SUBATOMIC STRUCTURE
• The experiments of Ernest Rutherford in the early
1900s, showed that matter consisted of small, highly
concentrated, points of matter (the nucleus) surrounded
by vast areas of empty space (the areas where electrons
exist).
• This is called the “Empty Space Model” of the atom.
• Rutherford shot high energy alpha particles at a gold
foil. The alpha particles acted as “bullets”. Most all the
alpha particles went straight through. A few were
deflected.
• From this experiment, Rutherford concluded that tiny
points of concentrated mass, distributed in mostly
empty space, was the fundamental structure of matter.
RUTHERFORD’S EXPERIMENT
(A CLOSE UP)
GOLD FOIL

PARTICLES
MOST OF THE ATOM
IS EMPTY SPACE
= NUCLEUS
A FEW
ALPHA
PARTICLES
ARE DEFLECTED
MOST TRAVEL
STRAIGHT
THROUGH THE
METAL
WHAT MAKES ONE ATOM DIFFERENT
FROM ANOTHER ?
• EACH ELEMENT HAS DIFFERING NUMBERS OF
PROTONS. THIS IS WHAT MAKES ELEMENTS
DIFFERENT, THE NUMBER OF PROTONS IT
CONTAINS.
• THE ATOMIC NUMBER OF AN ELEMENT TELLS US
THE NUMBER OF PROTONS IT CONTAINS.
ELEMENTS ON THE PERIODIC TABLE ARE
ARRANGED IN ROWS, LEFT TO RIGHT IN ORDER
OF INCREASING ATOMIC NUMBER. THEY START
WITH HYDROGEN, ATOMIC NUMBER 1,
FOLLOWED BY HELIUM, ATOMIC NUMBER 2,
LITHIUM ATOMIC NUMBER 3, ETC.
WHAT ABOUT THE NUMBER OF
NEUTRONS IN AN ATOM ?
• THE NUMBER OF NEUTRONS VARY FROM
ELEMENT TO ELEMENT. SOME ATOMS OF THE
SAME ELEMENT MAY HAVE DIFFERENT NUMBERS
OF NEUTRONS. ATOMS OF THE SAME ELEMENT
WITH DIFFERENT NEUTRON NUMBERS ARE
CALLED ISOTOPES.
• THE ATOMIC MASS TELLS US THE COMBINED
NUMBER OF PROTONS AND NEUTRONS IN THE
AVERAGE ATOM (ISOTOPE) OF THAT ELEMENT.
CALCULATING THE NUMBER OF
NEUTRONS IN AN ATOM
• THE ATOMIC NUMBER OF THE ELEMENT SODIUM
(Na) IS 11 AND ITS ATOMIC MASS IS 22.99. WE’LL
ROUND THIS NUMBER TO 23. SINCE THE ATOMIC
NUMBER TELLS THE NUMBER OF PROTONS,
SODIUM MUST HAVE 11 PROTONS. THE PROTONS
AND NEUTRONS TOGETHER EQUAL 23. BY
SUBTRACTION, SODIUM MUST HAVE 12 NEUTRONS
IN AN AVERAGE ATOM OF SODIUM.
• WHAT ABOUT AN ATOM LIKE CHLORINE? ITS
ATOMIC MASS IS 35.45. ITS ATOMIC NUMBER IS 17.
IT THEREFORE HAS 17 PROTONS, BUT
SUBTRACTING 17 FROM 35.45 GIVES 18.45. HOW
COULD AN ATOM HAVE .45 NEUTRONS??
HAVE YOU FIGURED OUT THE
ANSWER ??
• REMEMBER, THE ATOMIC MASS IS THE AVERAGE OF
THE DIFFERENT ISOTOPES OF THAT ELEMENT. NO ONE
ATOM HAS A MASS OF 35.45. INSTEAD, SOME
CHLORINE ATOMS HAVE MASSES OF 35, SOME 36, SOME
37.
• SO CHLORINE ATOMS OF MASS 35 HAVE 18 NEUTRONS,
THOSE OF MASS 36 HAVE 19 NEUTRONS AND THE MASS
37 ATOMS HAVE 20 NEUTRONS.
• THERE IS STILL A QUESTION HOWEVER. THE AVERAGE
OF 35, 36 AND 37 IS NOT 35.45, IT IS 36. WHY ISN’T 36
LISTED AS THE ATOMIC MASS NUMBER FOR CHLORINE
?
WHY NOT A MASS NUMBER OF 36 THEN ?
• IN ORDER TO GET 36 AS AN AVERAGE THERE MUST
BE EQUAL NUMBERS OF ATOMS OF ALL THREE
ISOTOPES OF CHLORINE PRESENT. THIS EQUAL
DISTRIBUTION IS RARELY TRUE FOR ANY
ELEMENT IN NATURE.
• HERE IS ANOTHER EXAMPLE. HYDROGEN ATOMS
OCCUR AS THREE DIFFERENT ISOTOPES,
HYDROGEN WITH AN ATOMIC MASS OF 1,
DEUTERIUM, THAT IS HYDROGEN WITH A MASS OF
2 AND FINALLY TRITIUM, HYDROGEN WITH A MASS
NUMBER OF 3. ON THE PERIODIC TABLE THE
ATOMIC MASS OF HYDROGEN IS LISTED AS 1.0079,
ALMOST 1. CAN YOU EXPLAIN WHY THE LISTED
MASS NUMBER IS SO CLOSE TO ONE INSTEAD OF
THE ARITHEMATIC AVERAGE OF TWO?
ARITHEMATIC AVERAGES AND WEIGHTED
AVERAGES ARE DIFFERENT. THE ATOMIC
MASS IS A WEIGHTED AVERAGE OF THE
ISOTOPES FOR THAT ELEMENT !
• HYDROGEN 1 (IT HAS 1 PROTON AND NO NEUTRONS)
REPRESENTS 99.985 % OF ALL HYDROGEN ATOMS
• HYDROGEN 2 (IT HAS 1 PROTON AND 1 NEUTRON)
REPRESENTS ONLY 0.015 % OF ALL HYDROGEN ATOMS.
• HYDROGEN 3 (IT HAS 1 PROTON AND 2 NEUTRONS)
REPRESENTS 0.0001 % , ALMOST NO HYDROGEN ATOMS.
• THE WEIGHTED AVERAGE CONSIDERS THAT MOST ALL
HYDROGEN ATOM HAVE A MASS OF 1 AND THEREFORE
THE NUMBER APPEARING ON THE PERIODIC TABLE IS
VERY, VERY CLOSE TO 1.00
THE ATOMIC MASS NUMBERS ON THE PERIODIC
TABLE THEN ARE WEIGHTED AVERAGES WHICH
ACCOUNT NOT ONLY FOR THE MASSES OF
DIFFERENT ISOTOPES, BUT ALSO ACCOUNTS FOR
ABUNDANCE (PERCENT) AT WHICH THEY OCCUR IN
NATURE !!
THE AVERAGES WHICH YOU ARE USED TO WORKING
WITH IN MATH CLASS ARE ARITHEMATIC AVERAGES
WHICH DO NOT ACCOUNT FOR ABUNDANCES.
SO FAR THEN, THE NUMBER OF PROTONS IN THE
NUCLEUS OF AN ATOM EQUALS THE ATOMIC
NUMBER AND THE NUMBER OF NEUTRONS EQUAL
THE ATOMIC MASS MINUS THE ATOMIC NUMBER
• WHAT ABOUT THE NUMBER OF ELECTRONS ??
• WELL, THIS DEPENDS ON WHETHER WE ARE
TALKING ABOUT A NEUTRAL ATOM OR AN ION !
• IN A NEUTRAL ATOM THE NUMBER OF ELECTRONS
AND PROTONS ARE EQUAL, SO THE NUMBER OF
ELECTRONS EQUALS THE ATOMIC NUMBER OF THAT
ATOM.
• IN THE CASE OF IONS THE NUMBER OF ELECTRONS
IS DIFFERENT THAN THE ATOMIC NUMBER.
WHAT IS AN ION ?
WHAT ARE THE TWO KINDS OF IONS ?
• IONS ARE ATOMS OR GROUPS OF ATOMS WITH EXTRA
OR MISSING ELECTRONS.
• ATOMS WITH EXTRA ELECTRONS ARE IONS WITH A
NEGATIVE CHARGE AND ARE CALLED ANIONS.
• ATOMS WITH MISSING ELECTRONS ARE IONS WITH A
POSITIVE CHARGE AND ARE CALLED CATIONS. IT IS
IMPORTANT TO UNDERSTAND HERE THAT CATIONS DO
NOT HAVE EXTRA PROTONS, THAT IS THEY DO NOT AND
CAN NOT GAIN PROTONS. IF THEY COULD THEY WOULD
BE COME A DIFFERENT ELEMENT. THE NUMBER OF
PROTONS AN ATOM CONTAINS MAKES THE ATOM WHAT
IS IT !!
LET’S DETERMINE THE ATOMIC STRUCTURE
FOR OXYGEN
• OXYGEN IS ELEMENT WITH AN ATOMIC NUMBER
OF 8 AND AN ATOMIC MASS NUMBER OF 16
(OXYGEN OCCURS AS THREE DIFFERENT
ISOTOPES 16, 17 AND 18. SINCE THE MASS
NUMBER IS SO CLOSE TO 16, MOST ALL OXYGEN
ATOMS (99.8 %) ARE ISOTOPE 16).
• THE MOST COMMON ATOM OF OXYGEN THEN
CONSISTS OF 8 PROTONS AND (16 – 8) OR 8
NEUTRONS IN THE NUCLEUS. IF THE ATOM IS
NEUTRAL IT THEN ALSO CONTAINS 8 ELECTRONS
EXTERNAL TO THE NUCLEUS.
WHEN ATOMS COMBINE TO FORM
MOLECULES THE ELECTRONS OF EACH
ATOM MUST FIRST INTERACT.
• HOW ARE THE ELECTRONS ARRANGED IN THE ATOM ?
UNDERSTANDING THIS HELPS US TO DISCOVER HOW
AND WHY ATOMS COMBINE!
• ELECTRON ARRANGEMENTS WITHIN ATOMS ARE
REFERRED TO AS ELECTRON CONFIGURATIONS.
• BEFORE WE CAN UNDERSTAND ELECTRON
CONFIGURATIONS, WE MUST FIRST UNDERSTAND HOW
THEY WERE DISCOVERED IN THE FIRST PLACE. THIS
REQUIRES THE USE OF A SCIENCE CALLED QUANTUM
MECHANICS.
BASIC CONCEPTS OF QUANTUM MECHANICS
• ELECTRONS EXIST IN AREAS OUTSIDE THE
NUCLEUS. THESE AREAS ARE CALLED ENERGY
LEVELS. YOU MIGHT HAVE HEARD OF THEM
BEFORE AS “SHELLS”. THERE ARE NUMEROUS
ENERGY LEVELS AT WHICH THE ELECTRON CAN
BE FOUND, EACH AT A PROGRESSIVE HIGHER
ENERGY.
• THESE LEVELS ARE ASSIGNED NUMBERS 1,2,3,
ETC. AS THE NUMBER INCREASES, THE ENERGY
STATE OF THE ELECTRON BECOMES HIGHER.
BASIC CONCEPTS OF QUANTUM
MECHANICS (CONT’D)
• AN ORIGINAL ATOMIC THEORY PROPOSED BY NEILS BOHR IN
THE EARLY 20TH CENTURY SUGGESTED THAT ELECTRONS
CIRCLE THE NUCLEUS OF ATOMS IN ORBITS SIMILAR TO THE
PATHS OF THE PLANETS AROUND THE SUN.
ELECTRON
ORBITS !!
NEILS BOHR
• A MOST IMPORTANT CONCEPT OF MODERN QUANTUM
THEORY IS HOWEVER, THAT ELECTRONS DO NOT MOVE
IN ORBITS ABOUT THE NUCLEUS OF THE ATOM !!
THE ENERGY LEVELS OF ATOMS ARE NOT ORBITS FOR
ELECTRONS. THEY ARE AREAS OF HIGH PROBABILITY
OF FINDING ELECTRONS.
BASIC CONCEPTS OF QUANTUM MECHANICS
(CONT’D)
• WHEN ENERGY (HEAT, ELECTRICITY, ETC.) IS
ADDED TO AN ATOM, THE ELECTRONS WITHIN
THE ATOM JUMP TO HIGHER ENERGY LEVELS.
• WHEN THE ELECTRONS FALL BACK TO THEIR
ORIGINAL ENERGY LEVEL, THEY RELEASE THE
ENERGY THAT THEY ABSORBED IN THE FORM OF
LIGHT.
• THEREFORE, IN ORDER TO UNDERSTAND THE
ELECTRONIC STRUCTURE OF THE ATOM WE
MUST FIRST UNDERSTAND THE NATURE OF
LIGHT ITSELF!
WAVES &
IRWIN SCHROEDINGER
QUANTUM MECHANICS GENIUS
ORBITALS
LIGHT – A WAVE AND A PARTICLE
• LIGHT MAY THOUGHT OF AS A WAVE IN SOME
CASES AND AS A PARTICLE IN OTHERS. WHICH
ONE IS IT REALLY? BOTH !!
• LET’S TALK ABOUT WAVES FIRST. IMAGINE A
WATER WAVE TO START. ALL WAVES HAVE THREE
BASIC PROPERTIES. CAN YOU NAME ONE?
• (1) WAVELENGTH
• (2) FREQUENCY
• (3) SPEED OR VELOCITY
MORE ABOUT WAVES
• WHAT IS WAVELENGTH ?
• THE DISTANCE REQUIRED FOR ONE COMPLETE WAVE TO
OCCUR. ITS SYMBOL IS THE GREEK LETTER ,  , “LAMBDA”
AND IT IS MEASURED IN METER PER WAVE. IT COULD BE
MEASURED FROM THE CREST OF ONE WAVE TO THE CREST
OF THE NEXT, OR THE TROUGH OF ONE TO THE NEXT, AS
LONG AS THE LENGTH OF ONE COMPLETE WAVE IS
MEASURED.
• WHAT IS FREQUENCY ?
• IT IS EXACTLY WHAT IS SAYS, HOW FREQUENTLY DO WAVE
COME BY. FOR EXAMPLE, HOW MANY WAVES HIT THE
SHORE IN A SECOND! THAT IS THE WAVE’S FREQUENCY. WE
USE THE GREEK LETTER, , “NU” AS THE SYMBOL FOR
FREQUENCY AND IT IS MEASURED IN WAVES PER SECOND.
( A WAVE PER SECOND IS CALLED A HERTZ)
MORE ABOUT WAVES (CONT’D)
• SPEED OR VELOCITY AS YOU PROBABLY KNOW, TELLS US
HOW FAR THE WAVE GOES IN A SECOND. THE WAVES THAT
WE WILL BE TALKING ABOUT, AS SAID BEFORE, ARE LIGHT
WAVES. THE SPEED OF LIGHT WAVES IS VERY, VERY FAST,
ABOUT 186,000 MILES PER SECOND !
• THAT IS 3.0 x 108 METER PER SECOND.
• “C” IS THE SYMBOL USED FOR THE SPEED OF LIGHT
(C = 3.0 x 108 METERS / SECOND)
MORE ABOUT WAVES (CONT’D)
• HOW ARE WAVELENGTH, FREQUENCY AND
THE SPEED OF A WAVE RELATED ?
•
•
•
•
•
•
THE UNITS FOR WAVELENGTH ARE METERS / WAVE
THE UNITS FOR FREQUENCY ARE WAVES / SECOND
THE UNITS FOR SPEED ARE METERS / SECOND
(METERS / WAVE) x (WAVES / SEC) = METERS / SEC
WAVELENGTH
x
FREQUENCY = SPEED

x

=
• REMEMBER C IS THE SPEED OF LIGHT
•
3.0 x 108 METERS / SECOND
C
VISIBLE AND INVISIBLE LIGHT
• MOST “LIGHT” IS NOT VISIBLE TO THE HUMAN EYE !
• ONLY ABOUT 7 % OF THE KNOWN KINDS OF LIGHT CAN
BE SEEN WITHOUT SPECIAL INSTRUMENTATION.
VISIBLE AND INVISIBLE LIGHT
• THE VISIBLE SPECTRUM INCLUDES ALL THE COLORS OF
THE RAINBOW, ROYGBIV, RED, ORANGE, YELLOW, GREEN,
BLUE, INDIGO AND VIOLET !
• EACH COLOR AND EACH KIND OF LIGHT CAN BE
INDENTIFIED BY ITS WAVELENGTH AND / OR FREQUENCY.
• THE RED END OF THE SPECTRUM HAS THE LONGEST
WAVELENGTH AND LOWEST FREQUENCY IN THE VISIBLE
RANGE.
• THE VIOLET END HAS THE SHORTEST WAVELENGTH AND
HIGHEST FREQUENCY.
• AS WAVELENGTH INCREASES, FREQUENCY DECREASES,
THEY ARE INVERSE TO EACHOTHER
•


VISIBLE AND INVISIBLE LIGHT (CONT’D)
• THE WAVELENGTH OF RED LIGHT IS APPROXIMATELY 7.20
x 10-7 METERS OR 720 NANOMETERS
• THE WAVELENGTH OF VIOLET LIGHT IS APPROXIMATELY
3.80 x 10-7 METERS OR 380 NANOMETERS
• INFRARED (BELOW RED) OR IR CONSISTS FREQUENCIES
LOWER THAN RED (AND  > 720 NM) AND ULTRAVIOLET
(ABOVE VIOLET) OR UV CONSISTS OF FREQUENCIES
HIGHER THAN VIOLET (AND  < 320 NM).
• ALTHOUGH BOTH INVISIBLE, INFRARED CAN BE FELT AS
HEAT AND ULTRAVIOLET FROM THE SUN CAUSES
SUNBURN.
• IN ORDER TO BE MEASURED, IR AND UV REQUIRE
DETECTORS TO BE USED
CALCULATIONS INVOLVING LIGHT WAVES
• THE WAVELENGTH OF GREEN LIGHT IS
APPROXIMATELY 5.5 x 10-7 METERS. WHAT IS ITS
FREQUENCY ?
• SOLUTION: WE KNOW  AND  ARE INVERSELY
PROPORTIONAL BY THE EQUATION
 x  = C AND C = 3.0 x 108 M / SEC
(5.5 x 10-7 M / WAVE)  = 3.0 x 108 M /SEC
 = 5.45 x 1014 WAVES / SEC OR HERTZ
CALCULATIONS INVOLVING LIGHT WAVES
(CONT’D)
• WHAT COLOR IS LIGHT OF A FREQUENCY 3.75 x 1014 HZ ?
• SOLUTION: WE KNOW THE RANGE OF VISIBLE LIGHT IS
BETWEEN RED ( = 7.2 x 10-7 METERS) AND VIOLET ( =
3.8 x 10-7 METERS). LET’S FIRST FIND THE  OF
FREQUENCY 3.75 x 1014 HZ !
•
 x  =
C
 (3.75 x 1014 HZ) = 3.0 x 108 METER /SEC
 = 8 x 10-7 METERS
THIS  IS LONGER THAN RED THEREFORE THE LIGHT IS
INFRARED AND INVISIBLE. IT HAS NO “COLOR”!
USING OUR KNOWLEDGE OF LIGHT TO
UNDERSTAND ELECTRONIC STRUCTURE IN ATOMS
• RECALL FROM OUR PREVIOUS INFORMATION:
WHEN ATOMS ABSORB ENERGY, ELECTRONS JUMP TO
HIGHER ENERGY LEVELS. WHEN THEY FALL BACK TO
THEIR ORIGINAL ENERGY LEVELS, THAT ABSORBED
ENERGY IS RELEASED AS LIGHT.
ANALYZING THIS EMITTED LIGHT ALLOWS US TO
DISCOVER THE ELECTRONIC STRUCTURE OF THE
ATOM!
BEFORE WE CAN DO THIS HOWEVER WE MUST FIRST
INVESTIGATE THE SECOND NATURE OF LIGHT, THAT IS
ITS PARTICLE NATURE !!
LIGHT PARTICLES, PLANCK AND PHOTONS
• PARTICLES OF LIGHT ARE CALLED “PHOTONS”. THESE
ARE “PACKAGES” OF LIGHT ENERGY.
• MAX PLANCK WAS FIRST TO DISCOVER THE
RELATIONSHIP BETWEEN THE WAVE NATURE OF LIGHT
AND ITS PARTICLE NATURE.
• HE FOUND THAT THE ENERGY CONTENT OF LIGHT WAS
DIRECTLY RELATED TO THE FREQUENCY OF THE LIGHT
WAVE.
PHOTONS
• THE EQUATION THAT MEASURES ENERGY AS A
FUNCTION OF FREQUENCY IS:
ENERGY = A CONSTANT x FREQUENCY
E
=
h
x

MR. PLANCK
WERE h IS A CONSTANT CALLED
PLANCK’S CONSTANT (6.63 x 10-34 JOULES SEC / PHOTON)
THE PHOTOELECTRIC EFFECT AND PHOTONS
EXPERIMENTAL PROOF OF THE PARTICLE NATURE
OF LIGHT IS FOUND IN THE PHOTOELECTRIC EFFECT.
WHEN LIGHT IS SHONE ON AN ACTIVE METAL SUCH
AS POTASSIUM ONLY LIGHT OF A CERTAIN MINIMUM
FREQUENCY WILL CAUSE ELECTRONS TO LEAVE THE
METAL SURFACE NO MATTER WHAT THE INTENSITY
OF THE LIGHT SOURCE. BASED ON THIS EXPERIMENT
THE ENERGY OF LIGHT IS FOUND TO BE CONTAINED
IN PACKAGES CALLED PHOTONS. THE ENERGY OF
THE PHOTONS OF A SPECIFIC KIND OF LIGHT IS
DIRECTLY RELATED TO ITS FREQUENCY.
THE PHOTOELECTRIC EFFECT EXPERIMENT
ONLY CERTAIN MINIMUM FREQUENCIES OF LIGHT
FREE THE ELECTRONS FROM THE METAL
(ONLY PHOTONS WITH ENOUGH ENERGY)
PHOTONS
VOLTMETER
ELECTRONS
PICKUP
WIRE
POTASSIUM METAL
BATTERY
LIGHT PARTICLES, PLANCK AND PHOTONS
• RECALL THAT RED LIGHT HAS A WAVELENGTH OF
7.2
x 10-7 METERS AND A CORRESPONDING FREQUENCY OF
4.2 x 1014 HZ.
• VIOLET LIGHT HAS A WAVELENGTH OF 3.8 x 10-7 METERS
AND A CORRESPONDING FREQUENCY OF 7.9 x 1014 HZ.
•
E = h x 
• USING PLANCK’S EQUATION, WE SEE THAT VIOLET
CONSISTS OF HIGHER ENERGY PHOTONS BECAUSE OF
ITS HIGHER FREQUENCY THAN DOES RED LIGHT WHICH
IS OF A LOWER FREQUENCY.
LIGHT PARTICLES, PLANCK AND PHOTONS
(CONT’D)
• SAMPLE PROBLEM:
• WHAT IS THE ENERGY OF A PHOTON OF UV LIGHT WITH
WAVELENGTH,  = 3.0 x 10-7 METERS ?
• SOLUTION:
 x  = c
(3.0 x10-7)  = 3.0 x 108
 = 1.0 x 10 15 HZ
• REMEMBER: E = h x  AND
• FIRST  x  = c,
•
• E = h x 
• E = (6.63 x 10-34 JOULES SEC / PHOTON) x 1.0 X 1015 HZ
E = 6.63 x 10-19 JOULES / PHOTON OF UV LIGHT
LIGHT PARTICLES, PLANCK AND PHOTONS
(CONT’D)
• IN ADDITION TO LIGHT VERY HIGH VELOCITY
SUBATOMIC PARTICLES (SUCH AS ELECTRONS)
ALSO HAVE OBSERVEABLE WAVE PROPERTIES.
THE WAVELENGTH OF THESE PARTICLE CAN
BE CALCULATED USING THE DEBROGLIE
EQUATION:
• = h/mxv
WHERE h = PLANCK’S CONSTANT
iiIF
YOU’RE
MOVIN’
YOU’RE
WAVEN’
DUDE!
(6.63 x 10-34 JOULE SEC/ PHOTON)
m = MASS IN KILOGRAMS
v = VELOCITY IN METERS / SEC
De Broglie
LIGHT PARTICLES, PLANCK AND PHOTONS
(CONT’D)
• SAMPLE PROBLEM:
ALL MOVING OBJECTS HAVE WAVELENGTHS EVEN
EVERYDAY OBJECTS, HOWEVER LARGE MASS
PARTICLES EXHIBIT VERY SHORT WAVELENGTHS.
FOR EXAMPLE: WHAT IS THE WAVELENGTH OF A 60 Kg
RUNNER WHO IS MOVING AT 10 METERS / SECOND?
 = h / m x v,  = (6.63 x10-34) / (60 x 10)
 = 1.11 x 10-36 METERS
(A VERY, VERY SMALL WAVELENGTH)
PLANCK’S EQUATION AND ELECTRON ENERGIES
• WHEN LIGHT IS EMITTED BY ENERGIZED ATOMS IT CAN BE
SEPARATED INTO ITS COMPONENT WAVELENGTHS AND
FREQUENCIES. THESE FREQUENCIES ARE CONVERTED TO
ENERGIES USING PLANCK’S EQUATION.
• FROM THIS DATA THE ENERGY STATE OF ELECTRONS
WITHIN THE ATOM CAN BE DETERMINED !
• USING THIS INFORMATION, AN ENERGY LEVEL DIAGRAM
FOR ELECTRONS CAN BE CONSTRUCTED.
Component wavelengths
Energized Hydrogen gas
Prism
ENERGY LEVEL DIAGRAM FOR ELECTRON
STRUCTURE OF ATOMS
• CALCULATIONS REGARDING ELECTRON ENERGIES
•
•
•
•
RESULTED IN THE DISCOVERY OF QUANTUM NUMBERS
WHICH LEAD TO ENERGY LEVELS (SHELLS), ATOMIC
ORBITALS (SUBSHELLS) AND ELECTRON POPULATION OF
ATOMS
ENERGY LEVELS ARE ENERGY STATES WITHIN ATOMS
WERE ELECTRONS HAVE A HIGH PROBABILITY OF BEING
FOUND
ORBITALS ARE ENERGY STATES THAT EXIST AT THE
ENERGY LEVELS WHERE ELECTRONS CAN BE LOCATED.
ENERGY LEVELS ARE DESIGNATE BY INTEGERS
BEGINNING AT 1 (THE LOWEST ENERGY STATE) AND
RANGE UPWARD THROUGH 2, 3, 4, ETC.
ORBITALS ARE DESIGNATED BY LETTERS, S, p, d AND f.
ENERGY LEVEL DIAGRAM FOR ELECTRON
STRUCTURE OF ATOMS (CONT’D)
• IT HAS BEEN DETERMINED THAT ORBITALS ARE
ARRANGED AT EACH ENERGY LEVEL IN A VERY SPECIFIC
PATTERN.
•
•
•
•
•
N IS USED TO REPRESENT ENERGY LEVELS
AT ENERGY LEVEL 1 (n = 1), ONLY AN S ORBITAL OCCURS
AT ENERGY LEVEL 2 (n = 2), S & p ORBITALS OCCUR
AT ENERGY LEVEL 3 (n = 3), S, p & d ORBITALS OCCUR
AT ENERGY LEVEL 4 (n = 4), S, p, d & f ORBITALS OCCUR
ENERGY LEVEL DIAGRAM FOR ELECTRON
STRUCTURE OF ATOMS (CONT’D)
• ORBITALS OF EACH TYPE OCCUR IN DIFFERENT
GROUPINGS. S ORBITAL OCCUR ONLY AS SINGLE
ORBITALS WHILE p ORBITALS OCCURS AS A GROUP OF
THREE, d ORBITALS IN FIVES AND f ORBITALS IN SEVENS.
• ORBITAL TYPE
NUMBER OF ORBITALS
MAX. # e- *
s
1
2
p
3
6
d
5
10
f
7
14
*EACH
ORBITAL CAN CONTAIN A MAXIMUM OF 2
ELECTRONS HOWEVER ORBITALS MAY HAVE NO
ELECTRONS OR BE HALF FILLED WITH ONE ELECTRON.
ENERGY LEVEL DIAGRAM FOR ELECTRON
STRUCTURE OF ATOMS (CONT’D)
• USING THE INFORMATION PROVIDED BY QUANTUM
MECHANICS, THE SHAPES EACH TYPE OF ATOMIC ORBITAL
WITHIN THE ATOM HAS BEEN DESCRIBED.
ENERGY LEVEL DIAGRAM FOR ELECTRON
STRUCTURE OF ATOMS (CONT’D)
• IN ADDITION TO ENERGY STATES AND ORBITAL SHAPES, A
COMPLETE ENERGY LEVEL DIAGRAM FOR THE ATOM HAS BEEN
DETERMINED USING QUANTUM MECHANICAL DATA.
• THIS DIAGRAM IS USED TO PREDICT THE ELECTRONIC
CONFIGURATIONS OF ATOMS
SUMMARY
• ATOMS ARE COMPOSED OF A NUCLEUS AND EXTERNAL
ELECTRONS
• THE ATOMIC NUMBERS ALLOWS US TO DETERMINE THE
NUMBER OF PROTONS AND ELECTRONS IN AN ATOM
• THE ATOMIC MASS ALLOWS US TO DETERMINE THE NUMBER
OF NEUTRONS IN THE MOST COMMON ISOTOPE OF AN
ELEMENT
• ELECTRONS HAVE BOTH WAVE AND PARTICLE NATURES
• THE PROPERTIES OF WAVES INCLUDE WAVELENGTH,
FREQUENCY AND SPEED
• THE EQUATION:  x  = c RELATES THE THREE
PROPERTIES
• LIGHT ENERGY IN THE FORM OF PHOTONS CAN BE
CALCULATED BY PLANCK’S EQUATION: E = h x 
• ANALYZING LIGHT EMITTED BY ATOMS CAN ALLOW US TO
DETERMINE THE ELECTRONIC STRUCTURE OF THE ATOM
SUMMARY (CONT’D)
• QUANTUM MECHANICS TELLS US THAT
ELECTRONS ARE FOUND AT ENERGY LEVELS IN
ORBITALS WITHIN THE ATOM
• ENERGY LEVELS AND ORBITALS ARE SETUP IN A
VERY SPECIFIC MANNER IN THE ATOM
• ATOMIC ORBITALS INCLUDE S, p, d, AND f
ORBITALS. EACH IS A DIFFERENT SHAPE AND
CAN ACCOMMODATE DIFFERENT NUMBERS OF
ELECTRONS
• AN ENERGY LEVEL DIAGRAM FOR ATOMS CAN
BE OBTAINED FROM QUANTUM MECHANICS AND
IT ALLOWS US TO ACCURATELY DESCRIBE THE
ELECTRONIC STRUCTURE OF ATOMS
SUMMARY (CONT’S)
• OUR NEXT PROGRAM WILL SHOW HOW TO USE
THE ENERGY LEVEL DIAGRAM FOR VARIOUS
ATOMS AND IONS.
• TG