Unit 5 : Atomic Structure

Unit 5 : Atomic Structure

Dalton’s Atomic Theory(1803)
Elements are made up of tiny invisible particles called atoms. Atoms of the same element are identical. Atoms of different elements are different. Compounds are formed when atoms combine. Each compound has a specific number and kinds of atom. Chemical reactions are rearrangement of atoms. Atoms are not created, destroyed, nor broken apart.

Experiments to determine what an atom was
J. J. Thomson- used Cathode ray tubes Clip of Cathode Ray Tube

Thomson’s Experiment Voltage source - +

- + Thomson’s Experiment Voltage source
Passing an electric current makes a beam appear to move from the negative to the positive end.

Thomson’s Experiment Voltage source By adding an electric field

Voltage source + - By adding an electric field, he concluded that the particles were Positively charged Negatively charged Not charged Some negative and some positively charged

Thomsom’s Model Found the electron.
Spread out + charge Found the electron. Couldn’t find positive (for a while). Said the atom was like plum pudding (p. 101) (or Jello with fruit) A bunch of positive stuff, with the electrons able to be removed.

Rutherford’s Experiment
Used _________to produce alpha particles. Aimed alpha particles at gold foil by drilling hole in _______ container. Since the mass is evenly distributed in gold atoms alpha particles should go straight through. Used gold foil because it could be made atoms thin.

Rutherford’s Experiment
After watching video, label the parts of his set-up on your handout.

Florescent Screen Lead block Polonium Gold Foil Alpha Particle

What he expected

Because

Because, he thought the positive charge (and mass)was evenly distributed in the atom. (according to Thomson’s Model)

What he got

Small dense, positive piece at center.
How he explained it Atom is mostly empty Small dense, positive piece at center. + Rutherford just concluded that atoms have: Electrons Protons Neutrons a Nucleus

How he explained it Atom is mostly empty Small dense, positive piece at center. Alpha particles are deflected by it if they get close enough. +

Modern View The atom is mostly empty space. Two regions
Nucleus- protons and neutrons. Electron cloud- region where you might find an electron.

Sub-Division of an Atom
Atom has two parts: Electron Cloud - space where electrons travel - small, dense Center of atom Nucleus

Size of Atoms Very small, drawing a line across a penny would cross over _______________ atoms Diameter of 1 atom = 1x10-8 cm --or-- 350,000 4 million 63 million 810 million 1 Angstrom (Å) -- or – 10 nanometers

Size of Atoms Most of atom is electron cloud
Nucleus is a very tiny portion of atom Ratio, If an atom were the size of a football stadium, the nucleus would be the size of a pea !

Sub-Atomic Particles ELECTRONS: Negatively charged
Rotate around nucleus All electrons are identical Mass: insignificant compared to nucleus-0

Sub-Atomic Particles Protons:
Positively charged - same magnitude as e- Located in nucleus Mass: “heavy” compared to an electron All protons are identical If proton were 1 kg, electron would be 1 cg Mass = 1 atomic mass unit (amu)

Sub-Atomic Particles Neutrons: Neutral - no charge Located in nucleus
All neutrons are identical Mass: same as proton ( 1 amu) . Proton Neutron Electron 1 amu 1 amu 0 amu

What the Numbers on Periodic Table Tell us about the Atom
Atomic Number H 1 1.0079 The number of Protons Equal to the number of electrons if atom is neutral Protons determine identity of Element Number of Protons does not change

What the Numbers on Periodic Table Tell us about the Atom
1 1.0079 Atomic Mass

Mass Number: The Mass of an Atom (NOT found on Pd Table)
Mass of an atom = mass of the nucleus Determined by counting Protons & Neutrons Mass Number = # of Protons # of Neutrons Ex: Oxygen Ex: Beryllium # of protons = 8 # of protons = 4 + + # of neutrons = 8 # of neutrons = 5 Mass Number = 16 Mass Number = 9

Your Turn: Mass Number Ex: Potassium # of protons = 19 +
# of neutrons = Mass Number = 40 Enter the # of neutrons into your clicker

Your Turn: Mass Number Ex: Potassium # of protons = 19 +
# of neutrons = 21 Mass Number = 40

More Examples Ex: Oxygen Ex: Oxide ( ) O2- # of protons = 8
# of electrons = 8 # of electrons = 10 # of neutrons = 8 # of neutrons = 8 Mass Number = 16 Mass Number = 16 How many neutrons and electrons ?

Your Turn: Number of Electrons
Ex: Bromide (Br-) # of protons = 35 # of electrons = Complete the Chart # of neutrons = Mass Number = 79 How many protons, then enter the # of neutrons into your clicker?

Ex: Bromide (Br-) # of protons = 35 # of electrons = # of neutrons = 44 Mass Number = 79 Enter the # of electrons.

Ex: Bromide (Br-) # of protons = 35 # of electrons = 36 # of neutrons = 44 Mass Number = 79

Ex: Magnesium (Mg+2) # of protons = 12 # of electrons = Complete the Chart # of neutrons = 13 Mass Number = 25 Enter the # of neutrons in clicker

Ex: Magnesium (Mg+2) # of protons = 12 # of electrons = 10 # of neutrons = 13 Mass Number = 25 Enter the # of electrons in clicker

Welcome Back ! Check Your Posted Grades
Look at 2nd Marking Pd CLC’s and Verify Total Look at Separate CLC Gradesheet for 3rd MP Pick up your “Clicker” and Log in. Tell Your Lab Partner what “Mass Number” means Enter in clicker the # of Neutrons that are in Mg-25

Welcome Back ! Have you or your partner Log in to a nearby computer.
Ask your partner what “Atomic Number” means Tell Your Lab Partner what “Mass Number” means Enter in clicker the # of Neutrons that are in Mg-25

Warm-Up Ex: Magnesium (Mg+2) # of protons = 12 # of electrons = 10
# of neutrons = 13 Mass Number = 25 Enter the # of electrons in clicker

Lesson Review The _____ is the total mass of a single atom.
Atomic Mass Mass Number Atomic Number Number of Protons

Lesson Review The _____ is always equal to the number of protons.
Atomic Mass Mass Number Atomic Number Number of Neutrons

Lesson Review The _____ is equal to the number of protons and neutrons
Atomic Mass Mass Number Atomic Number Number of Protons

Lesson Review The _____ is the difference between the number of protons and the number of electrons Number of Neutrons Atomic Number Mass Number Charge

Time for Practice: Log in to Moodle and go to the pHet Activity called “Build an Atom” Choose Game at Level 4

Isotopes Different “Varieties” of an Atom
Isotopes are atoms of the same element, but with different #’s of Neutrons. Therefore, they have different Mass #’s. Isotopes are Chemically Identical About 300 Stable Isotopes of the first 83 elements exist, plus several hundred more unstable isotopes What element did you get for the 5th and 6th row on your chart? Are these atoms both identical? Was Dalton right in all of his postulates?

What has to be the same for all three?
Isotopes of Hydrogen: What has to be the same for all three? What will be different? If there are all Hydrogen, what has to be the same? What is different? 1 proton 1 proton 1 proton 0 neutrons 1 neutron 2 neutrons Mass #: 1 amu 2 amu’s 3 amu’s

Have you ever heard of “tritium” before?
Isotopes of Hydrogen: Hydrogen-1 Mass Number Hydrogen-2 Hydrogen-3 “Protium” “Deuterium” “Tritium” If there are all Hydrogen, what has to be the same? What is different? 1 proton 1 proton 1 proton 0 neutrons 1 neutrons 2 neutrons Mass #: 1 amu 2 amu’s 3 amu’s

Isotopes of Hydrogen: Hydrogen-1 Hydrogen-2 Hydrogen-3 “Protium”
“Deuterium” “Tritium” If there are all Hydrogen, what has to be the same? What is different? 1 proton 1 proton 1 proton 0 neutrons 1 neutrons 2 neutrons Mass #: 1 amu 2 amu’s 3 amu’s

Naming Isotopes The hydrogen isotope with 0 neutrons can be written as hydrogen-1 or 1H Mass Number C 14 6 How many Neutrons? Number of Protons

Your Turn: Writing Isotopes
Sb 124 51 -3 How many of each particle are in this isotope: A 48 protons 51 electrons 124 neutrons B 51 protons 48 electrons 73 neutrons C 51 protons 51 electrons 124 neutrons D 51 protons 54 electrons 73 neutrons

Your Turn: Writing Isotopes
The following element has how many ______ protons ______ electrons ______ neutrons 51 54 73 Sb 124 -3 51

Atomic Mass Time for Grade Check
Look at your grade sheet and Calculate the Average of your grades for each unit Is this your actual grade? Grade = Unit1*(Weight) + Unit2*(Weight)…. If a football team had 20 players and 19 weighed 200 lbs, but the kicker weighed 100lbs, what is the average weight? Do any hydrogen atoms have a mass of ?

Atomic Mass Use this formula to calculate grade
Grade = Unit1*(Weight) + Unit2*(Weight)…. If a football team had 20 players and 19 weighed 200 lbs, but the kicker weighed 100lbs, what is the average weight? Do any hydrogen atoms have a mass of ?

Atomic Mass The AVERAGE mass of an atom of that element
Weighted according to the abundance of each Isotope Ex: Football team If a football team had 20 players and 19 weighed 200 lbs, but the kicker weighed 100lbs, what is the average weight? Do any hydrogen atoms have a mass of ?

Abundance of Hydrogen Isotopes:
“Protium” “Deuterium” “Tritium” Mass = 1 amu Mass = 2 amu Mass = 3 amu If there are all Hydrogen, what has to be the same? What is different? 99.985% 0.015% 1 x 10-16% Average Mass = amu = Atomic Mass

Atomic Mass The AVERAGE mass of an atom of that element
Weighted according to the abundance of each Isotope Ex: Football team Why are 99% of hydrogen atoms H-1? If a football team had 20 players and 19 weighed 200 lbs, but the kicker weighed 100lbs, what is the average weight? Do any hydrogen atoms have a mass of ?

Pre-Knowledge Check Get out your Atomic Structure Pre-Quiz and correct any incorrect answers you might have

“Science Sense” is Tingling
Alert: “Science Sense” is Tingling Nuclear Stability Rutherford says that nucleus is incredibly dense and small. We now know that the nucleus consists of a bunch of individual protons Nucleus consists of a bunch of protons crammed together in a tiny area

Nuclear Stability Protons Repel other protons. +
Putting Protons together in a tiny nucleus is unstable because of this repulsion Neutrons act as “glue” to hold the protons together in the nucleus + + + When Rutherford said that all the protons were crammed into a tiny space, my science sense starts tingling. Why? Stable

Ratio of Neutrons to Protons
For smaller elements (1-30), about 1 neutron per proton seems to work best 1:1 ratio Ex: Oxygen Ex: Beryllium Protons = 8 Protons = 4 When using glue, you need just the right amount. Too much or too little will result in things not holding together. Neutrons = 8 Neutrons = 5 Most Stable Isotope has 1:1 Ratio Most Stable Isotope has close to 1:1 Ratio

“Science Sense” is Tingling
Alert: Nuclear Stability “Science Sense” is Tingling Therefore, without this proper ratio of neutrons, the nucleus would be unstable and fly apart. So how can Hydrogen-1 exist as a stable atom?

Ratio of Neutrons to Proton
As the elements get larger (>30), a higher ratio of neutrons is needed. Example: Mercury has 80 protons, but around 120 neutrons are needed to hold them together 120 / 80 is a 1.5 : 1 ratio.

Your Turn: Predicting Stability
Who would more likely be stable? Phosphorous – 15 Phosphorous – 31 Phosphorous – 44 Phosphorous – 58 Protons Neutrons 15 15 16 15 29 15 43

Your Turn: Predicting Stability
Who would more likely be stable? 74W 150W 184W 225W Protons Neutrons 74 74 76 74 110 74 151

Radioactivity After element # 83, the repulsive force of so many protons is so strong that no amount of neutrons will hold nucleus together permanently Thus, no stable isotopes exist for these elements These elements are called radioactive elements The nucleus breaks apart and pieces of radiation come flying out

Types of Radioactive Decay
Alpha Particle (α) – positively charged Beta Particle (β) - negatively charged Gamma Radiation (γ)- no charge

Alpha (α ) Decay 240 236 4 Pu U He + 94 92 2

Your Turn: Alpha Decay Write down your description of what happens during alpha decay

Beta (β ) Decay 228 228 Ra Ac e + 88 89 -1

Your Turn: Beta Decay Write down your description of what happens during beta decay

Gamma (γ ) Radiation Gamma Radiation is NOT a particle
It is Electromagnetic Radiation given off during Alpha or Beta Decay

Your Turn: Decay Equations
Write an equation of the alpha decay of Polonium-214 Write an equation of the beta decay of the Lead-210 214 210 4 Po Pb He + 84 82 2 210 210 Pb Bi e- + 82 83 -1

Comparison of Radiation
Bone Skin Organs Tissue

Your Turn: Radiation Comparison
Write a few sentences describing the penetrating ability and harmfulness of the three types of radiation

Half-Life 16 5 seconds 1st half-life 8 5 seconds 2nd half-life 4
3rd half-life Red Balls have a 5 second half-life 2

Half-Life Add applications of half-life Carbon-14 dating
Radioactive Waste Assumptions & Limitations Calibration and validation Interpolating vs extrapolating Other radiodating – age of the earth & universe

Selected Answers to Page 11 & 12
1) nucleus 2) Strong nuclear 3) stable 4) Radioactive (unstable) 5) Mass 6) Nuclear (radioactive) 7) It can only be used to date organic things 9) Protons repel each other, so they would fly apart 11) 42He 12) 0-1e 13) 42He 14) 14) 21084Po -> 20682Pb +42He 15) 31H -> 32He +0-1e 16) 23090Th -> 22688Ra + 42He 17) B 18) B 19) A 20) D

Answers to Page 13 & 14 Np Pu e U Th He 1) 0.0313 kg 3) 2.5 hr
8*) mol (don’t panic if you didn’t get this one) 2) 23,000 years 4) 90 years 7) 26 ug 9) 9 x 10-7 g 10) 160 sec. To Electrons 238 238 1) Np Pu e + 93 94 -1 238 234 4 2) U Th He + 92 90 2

Nuclear Fission U Kr Ba n 3 235 92 94 56 36 139 + 1
Fission is when a large, unstable nucleus breaks apart into 2 similar-sized nuclei 235 92 94 56 U Kr 36 Ba 139 + n 1 3 Gives off a HUGE amount of energy!

Uses for Nuclear Fission
Atomic Bombs are an uncontrolled fission reaction Nuclear Power plants use a controlled fission reaction Energy produced by nuclear reactions is HUGE! 1 Uranium pellet (2 oz) produces as much energy as: 17,000 cubic feet of natural gas 1,780 pounds of coal 149 gallons of oil A nuclear bomb can release about 1-20 million times more energy than the same mass of TNT

Advantages of Nuclear Fission
The Good News! Very efficient … a little bit of fuel makes a lot of energy Nuclear Power Plants do not pollute! (No NOx, SOx, or CO2) Reactors do not have enough uranium for an uncontrolled chain reaction. (subcritical mass) They will never explode like a nuclear bomb

Disadvantages of Nuclear Fission
The Bad News Stuff left after fission reaction is unstable (“Dirty”) Nuclear bombs affect area for miles around blast with radiation which takes decades to diminish Radioactive Waste – What do we do with it? Dangerous for 1000’s of years An accident could release radioactive material Chernobyll Reactor is housed in a containment unit to prevent this

Why did Doc Oc want the tritium?

What is nuclear fusion? Fusion is when 2 small nuclei combine to make a single, larger nucleus

What is nuclear fusion? Fusion reactions occur on stars (the sun)
This is source of energy given off by stars Fusion rxns make new elements H + H  He

Why the big deal over nuclear fusion?
Like fission, it produces lots of energy. (Even more per mass of fuel used) Fusion would be MUCH SAFER than fission Products are “clean” – not radioactive Accidents are much less likely and less dangerous (it can’t meltdown)

Are we close to using nuclear fusion?
Hydrogen Bombs use nuclear fusion (not dirty) In over 50 years of trying, still no controllable production of energy by fusion Since like charges repel, positively charged nuclei repel each other Extremely high speeds are needed to overcome repulsion – Temperature must be 40,000,000 K Would you predict it to be easy or hard to fuse two nuclei together? Why?

High temps would obliterate anything used to try to contain the reaction (metal, concrete walls) Can use high-powered lasers to try to get up to extremely high temperatures Tokamak – device that uses a magnetic field as the “wall” to try to contain the reaction

Joint European Torus (JET) Tokamak in Oxfordshire, UK

Reactors do exist, but currently use more energy than they produce. Hopefully by 2010 we will “break even” Possible major source of power in world by 2050

Revision: Law of Conservation of Matter and Energy
During both fission and fusion, Mass IS LOST The mass that is lost is transferred into HUGE amounts of energy (E=MC2) One little pellet of Uranium can produce as much energy as 2000 pounds of coal This is why nuclear reactions give off such a HUGE amount of energy – lost mass changes into energy! Time to Check HW

Things Associated with Nuclear Chemistry
Mass Number Nuclear Fission Beta Decay Ion Atomic Mass Plum Pudding Model

Things Associated with Nuclear Chemistry
Alpha Particle Half-Life Isotope Atomic Number Ground State 1.5 to 1 Ratio

Understanding the Motion of Electrons
Do electrons just randomly move about the nucleus? If so, they could possess any given energy at any given point in time

Max Planck & The PhotoElectric Effect
Story of Trumpet & Guitar Max Planck & The PhotoElectric Effect When some metals are exposed to certain wavelengths of light, the electrons absorb the energy and are emitted. Other wavelengths of light show no effect Page 18B

Max Planck & The PhotoElectric Effect
Story of Trumpet & Guitar Max Planck & The PhotoElectric Effect This seemed to indicate that electrons in the atoms possessed specific energies and not just any random amount of energy.

(The Solar System Model)
Bohr Model of Atom Electrons “orbit” the nucleus in fixed, quantized energy levels Electrons exist only on these energy levels Electrons can “jump” up energy levels if a matching photon of energy is absorbed (excited state) 1 2 3

(The Solar System Model)
Bohr Model of Atom Electrons can “jump” up energy levels if a matching photon of energy is absorbed (excited state) Electrons give off energy when they “jump” back down to the more stable ground state. Ground State – when the electrons in an atom are arranged in the lowest possible energy level. 1 2 3

Further Evidence for Bohr Model
When heated, each element emits energy in certain wavelengths (neon lights) -- demo These energies given off can be separated by a spectroscope producing a line spectra Lithium Each line a specific amount of energy with a specific wavelength Each line represents a specific jump that an electron is making within that atom

Each element produces its own unique spectrum
Each element has energy levels in different places, so they have different ‘jumps’ Each element produces its own unique spectrum Sodium Mercury Lithium Hydrogen

Atomic Line Spectra

Spectrum are often called the “fingerprint” of an element
Use spectra to determine what gases are in stars Demo – flame test

Jumping of Electrons Show possible jumps for Elliot

This chart shows all the possible jumps an electron of hydrogen can make

Each jump produces a specific amount of energy with a specific wavelength

Each arrow represents a jump an electron can make
Energy Level #3 Energy Level #2 This arrow represents an electron jumping from level 3 to 2

Each arrow represents a jump an electron can make
This jump is labeled “a” in the “Balmer Series” Energy Level #3 Energy Level #2

Hydrogen Balmer Series
Each jump produces a specific amount of energy with a specific wavelength 400 500 600 700 e d c b a Hydrogen Balmer Series “a” in the “Balmer Series” An electron jumping from level 3 to 2 will always give off energy with a wavelength of 650 nm (red light)

Warm-Up: Turn to page 28 in your packet and determine the wavelength of the energy produced when a hydrogen electron jumps from energy level # 6 to 3 B) If 1 Angstrom = 1 x 10-9 m, what is this wavelength in meters?

What jump makes this blue?
400 500 600 700 e d c b a Hydrogen Balmer Series

Page 28 – jumps of hydrogen
HW – Page 29

Quantum Mechanical Model
Our Modern View of the Atom

Bohr Model vs Quantum Model
The electrons do not travel in fixed paths as Bohr suggested, however their motion is not entirely random either. The electrons have regions where have high probabilities of being found Space Orbital - area where an electron will be within 90% of the time.

Quantum Numbers The 4 Quantum Numbers are like an “address” describing the location of an electron No two electrons have the exact same set of quantum numbers

Principal Quantum Number (n)
Describes the energy level that electron is in Energy level represents average distance an electron is from nucleus The larger the energy level, the larger the orbital and farther away from nucleus electron is 1 2 3

Angular Quantum Number (l)
Sometimes called “Orbital” or “Azimuthal” Q.N. Describes which type of orbital electron is in. Orbitals are defined by their shape. Book page 142…..

S orbitals (l=0) Shaped like a sphere or ball
Only 1 present in each energy level

P orbitals (l=1) Shaped like an hourglass, dumbbell, peanut
“P’s come in 3’s” -- have three on an energy level

D orbitals (l=2) Four leaf clover shaped, Daisy, “Double-peanut”
How many? 5 on an energy level.

F orbitals (l=3) Too complex and variable to visualize shape How many?
7

Magnetic Quantum Number(ml)
Tells which “p” orbital electron is in. Named according to axis they are oriented along. Py Px Pz

Spin Quantum Number(ms)
Each orbital can hold up to 2 electrons 2 Electrons may occupy the same orbital only if they are spinning in opposite directions. +1/2 (or 1) - first electron in orbital -1/2 (or -1) - second electron in orbital “+” and “-” indicate direction, NOT CHARGE

Learning Check Give the quantum numbers for the second electron placed in a dumbbell-shaped orbital in the horizontal position in the 4th energy level.

Orbitals & Energy Levels
Not every energy level has every orbital: Energy Level Orbitals Present Max e- Capacity 1 2 3 4 s 2 s,p 8 s,p,d 18 s,p,d,f 32

HomeWork – due tomorrow
Complete Page 21 & 22 Complete Pages 14B & 14C

Orbital “Order of Filling”

Shortcut Electron Config

Looking at the Pd Table (special no rule-breaker version)
p-Block s-Block d-Block

Looking at the Pd Table s-Block p-Block d-Block s1 p6 s2 p1

Your Turn: Shorthand Config
Do Shorthand Electron Configuration for: Sr Mo Sb

What’s the highest energy level that has e’s
3. Electron Dot Notation Electron dot notation shows only outer shell (valence) e’s Valence electrons are the outermost electrons in an atom – or - the electrons in the highest energy level Example: Oxygen 1s22s22p4 6 valence electrons What’s the highest energy level that has e’s Outer Shell How many valence e’s

3. Electron Dot Notation Example: Ge 1s22s22p63s23p64s23d104p2 Inner Shell 4 valence electrons Outer Shell Can d orbital electrons ever be in the outer shell? What’s the highest energy level that has e’s How many valence e’s

What elements have octets?
Electron Dot Notation Only s and p electrons can ever be in outer shell It takes __ electrons to fill the outer shell A filled outer shell is called an octet An octet is the most stable configuration an atom can have Noble Gases have octets 8 What elements have octets?

1 2 # of valence e’s 3 4 5 6 7 8

How many valence e’s does sulfur have?

How many valence electrons?
Electron Dot Notation S How many valence electrons? S 3s 3p

Electron Dot Notation S Unpaired electron Electron Pair

Electron Dot Notation 5 8 X 7 1 4 2 6 3

Your Turn: Electron Dot
Do the electron dot notation for the elements listed on the top part of page Also – tell how many pairs and unpaired electrons each element has

The following slides are generally not covered in CP Chem
Don’t worry about the following unless instructed to.

Order of Filling “Rule Breakers”
The Reasons: Having a filled energy level is a very stable configuration (Noble Gases) Having a filled subshell is also extra stable Having a half-filled subshell is also a bit extra stable Ne 2s 2p Mg 3s 3p P 3s 3p

Who breaks the rules? Elements whose last d and f orbitals are 1 electron short of being filled or half filled Almost Filled 4s 3d Almost Half- Filled 4s 3d

What do they do? An electron is moved from the higher ‘s’ orbital and placed in the d orbital to fill or half-fill it s and p orbitals do not do this. The energy difference between them is too great. (see poster) 4s 3d Filler 4s 3d Half-Filler

Bottom Line: You will never have a final answer with d orbitals looking like this: Or this: 5s24d9 5s14d10 5s24d4 5s14d5

Order of Filling Rule Breakers
Go to Your Homework Identify any rule-breaker Write the correct configurations in

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