History of the Development of the Atomic Model, Part 1 AS Aim #1 Where did the idea of the atom come from?

Atomic Model of the Atom Models help us describe several things about an atom: –____________ – what its made of –__________________ – lets us determine how atoms interact with each other We will look at several models of the atom that build upon previous models The modern model of the atom is based on the work of many scientists, not just one!

Early Greek Theories Democritus 400 B.C. His theory: –everything is composed of "atoms", which are physically ___________________________; –are always ________________; –come in there are an __________________ of types, variety, and shapes Based his theory on _____________________

Early Greek Theories Aristotle 350 B.C Presented a modified earlier theory that matter was made of four “elements”; ______, ____, ______, and ________ Based his theory on reason, ______________ But… ____________________! __________________________ must be done to ensure theories hold up under scrutiny!

John Dalton’s Atomic Theory of the Atom Early 1800’s English teacher John Dalton –proposed a modern atomic model of structure ________ _______________________ _______________________ –Described elements as being composed of particles called _______________________ –_______________________ to a given element

Components of Dalton’s Model All matter is __________________ Atoms of an element _________________ Each element has ___________________ 4.Atoms of different elements combine in __________________ to form compounds. Think of H 2 0 vs H 2 O 2 5.Atoms are __________________________ 2 H 2 +O 2  2 H 2 O

Dalton’s Theory accounts for: The Law of Conservation of Mass –Mass cannot be ____________________ –Hydrogen + Oxygen = Water –2 grams + 16 grams = ______________ The Law of Constant Composition –elements combine in fixed ratios. –2 hydrogen + 1 oxygen = _______________ –2 hydrogen + 2 oxygen = _______________ PROBLEM – no clues in his model as to the _________________________ of the atom

Cathode Rays and Electrons By 1897, experiments suggested atoms are composed of subatomic particles –Subatomic particles - ________________ British physicist J.J. Thomson –Used a ________________________ and discovered particles he called ___________ –____________ are negatively charged –Mass of one electron only 1/1836 of a ________________

The Thomson Atomic Model “Plum pudding” model –an atom is a positively charged, jellylike mass with electrons “stuck” in it Did not _____________ Dalton’s model Built upon Dalton’s model –__________ positive and negative charges –_________________ to the charges

History of the Development of the Atomic Model, Part 2 AS Aim #2 – What is significance of the Gold Foil Experiment?

Ernest Rutherford’s Gold Foil Experiment In his experiment, he bombarded (hit) extremely thin gold foil with _____________ –a helium nucleus only (_______________) –has a __________________ –_______________________ (more later) Based on Thomson’s Theory: –Particles should bounce off the ___________________ or –Particles should stick to the negative electrons made up of Thomson’s “plums”

Experimental Results –Some alpha particles _______________ or __________________ –But some particles ____________________ the atom –Why?

Rutherford’s Conclusion –Most of the mass of the atom is concentrated in a ________________________________ –Electrons are present in the space ________________________________ –The typical model of the atom represented in the media is Rutherford’s model at the right –So most of the volume of an atom is ____________________

Bohr’s Atomic Model Rutherford didn’t say where electrons were __________________ Bohr said that electrons exist in _________ or _________________ n represents the energy level –Energy level n = 1, holds up to ___________ –Energy level n = 2, hold up to ___________ –Energy level n = 3, hold up to ____________ –Energy level n = 4, holds up to ___________

Bohr’s Experiment: –Bohr used hydrogen gas which he heated to ___________________ –He analyzed the light patterns using a device called a ___________________________ which separated the colors of light produced –In hydrogen, he found four specific ____________ of color

Bohr’s Theory: Bohr found that electrons moved from one energy level to another when they gained energy They released the energy as light (photons) In the lowest levels, or the ground state, to the excited state ____________________ ________________________ When electrons moved from the excited state back to the ground state, ______________

Bohr’s Theory: This energy appears as wavelengths (______________) _______________ Each element produces its own pattern of ______________ or _________________ This is because each has different numbers of electrons

Summary of History of the Atomic Model Democritus – came up with the word _____ Dalton – his original atom had no ________, neutrons, or ________ in it Thompson – used _______________ tubes to discover electrons and their charge Rutherford – his experiment shot _____________ at a piece of ____________ Bohr – used excited hydrogen atoms to produce ___________ in various colors, and proved electrons existed in different energy levels

History of the Development of the Atomic Model, Part 3 AS Aim #3: Where does the Modern Model of the Atom place electrons?

Modern Atomic or Wave Mechanical Model Bohr’s shell model at the right is not quite right either! Electrons actually exist in ________________________ around the nucleus, not in orbits like planets around the Sun As per the Modern Atomic Model Also known as the Wave Mechanical Model of the Atom

Modern Atomic or Wave Mechanical Model These locations are based on where they are most likely found, ________________ We call this arrangement an _____________________ ______________ are a three dimensional representation of principal energy levels

Each energy level (n) contains smaller areas called ____________ In the Periodic Table, each block represents a __________________ with electrons This is what gives the Periodic Table its _____________________ There are _______________ each labeled “s”, “p”, “d”, and “f”

Sublevels are further broken down into areas called ____________ Each orbital only holds two (2) electrons each maximum and has a _____________ Sublevel Number of orbitals Shape of orbitals Maximum # of electrons s1 Single round sphere p3 Three dumbbell shapes d5 Five dumbbell shapes f7 Seven dumbbell shapes

Orbital shapes affect –how the Periodic Table _____________ –how _______________ with each other

Look at the Periodic Table Count the elements across each block. How many elements are there in each? s sublevel block = ____ p sublevel block = ____ d sublevel block = ____ f sublevel block= ____ Each ____________________ in the Periodic Table represents 1 more electron being added

Simplified Electron Configurations: –____________________ surround an atom –____________________ are in each energy level –____________________ they exist in Atomic mass Atomic Number Symbol Electron Configuration (2 e- in 1 st level, 4 e- in 2 nd level) C

Basic Electron Configuration Electrons fill the lowest energy levels first (_______________) The electron configuration is a “code” for showing _______________ around an atom Element 1 st Shell 2 nd Shell 3 rd Shell 4 th Shell Electron Config He22 Na Br Ca

The Octet Rule of Electron Configs Why is calcium’s 3 rd shell not filled? It should take up to __________ in the 3 rd shell The Octet Rule –no atom can have more than 8 electrons in the _____________________ energy level –If more than 8 electrons in an energy level occurs, we push two up to the next energy level Element 1 st Shell 2 nd Shell 3 rd Shell 4 th Shell Electron Config Ca

The Octet Rule of Electron Configs Having 8 electrons in the valence shell also makes the ___________ This occurs in the last column of the Periodic Table, a group of elements called Noble _____ Very _____________ with other elements Element 1 st Shell 2 nd Shell 3 rd Shell 4 th Shell Electron Config Ne Ar Kr

Excited State Electron Configurations Excited state electrons can be shown by not filling the _________________ Electrons have ___________ to higher shells Element Ground state electron configuration Excited state electron configurations He21-1, Na , Br , Ca ,

Fill in the chart below for each element’s ground state electron configuration and one excited state configuration: Element Ground state configuration Excited state configuration K Mg O S N P Ar

Atoms + Electrons = Ions AS Aim #4 – Why are most elements “wannabees”?

HAIL THE MIGHTY VALENCE ELECTRONS! Most of chemistry is really all about electrons and where they go and stay All elements in the Periodic Table are “__________________________” (Group 18) –If an atom can gain or lose electrons, it can have the electron configuration as the noble gases These elements become stable when they form _________: –a gain or loss of electrons gives an _____________ –a __________ electrons creates a negative ion –a __________ electrons creates a positive ion

HAIL THE MIGHTY VALENCE ELECTRONS! Ions are atoms with a charge, or an unequal number of protons and electrons What is the charge on a proton? ______ What is the charge on an electron? ______ What is the charge on each of the following atoms: –5 protons and 5 electrons = ______________ –5 protons and 4 electrons = ______________ –5 protons and 6 electrons = ______________ –19 protons and 21 electrons = ______________

HAIL THE MIGHTY VALENCE ELECTRONS! Ions of opposite charge can thus form compounds Positive ions ________________ negative ions (___________________!) In compounds, as in atoms, charges must add _________________ Therefore: –A +1 ion bonds with a -1 ion ( = ____) –A +2 ion bonds with a -2 ion ( = _____) –A +2 ion bonds with two -1 ions (+2 +(-1x2))= ___)

Each of the atoms below want to be ions with a stable electron configuration of eight Determine how many electrons are gained or lost Write the new electron configuration Element Electron Config of atom Gained or lost e- Electron Config of ion K lost2-8-8 Mg lost2-8 O2-62 gained2-8 N2-53 gained2-8 Li2-11 lost2

Lewis Electron-Dot Diagrams Another way to represent _____________ Lewis Dot Diagrams shows the number of ______________________ Procedure –Write the symbol first –Use the Periodic Table to find the number of valence (outermost) electrons –Place two dots to represent the first electrons on top –Place the rest evenly around the atom

Lewis Electron-Dot Diagrams Example: draw the Lewis Dot for chlorine and for sodium Notice: chlorine __________ to be like a noble gas, sodium ________________

Name, Symbols, and Atomic Numbers AS Aim #5 – What does a chemical symbol tell us about an element?

Identifying Elements – Names, Symbols, and Atomic Numbers Every element (as well as its atoms) is associated with three unique identifiers –Names –Symbols –Atomic numbers (number of protons in an atom) – obtained from the periodic table Element Name Element Symbol Element Atomic Number HydrogenH1 SodiumNa11 GoldAu79

Identifying Elements – Names, Symbols, and Atomic Numbers Names –are based on –_______– like Einsteinium –________ – like Francium –________________ - like chlorine (comes from the Greek work chloros, or “yellow green”)

Identifying Elements – Names, Symbols, and Atomic Numbers Symbols Each element with permanent names have unique letters associated with them –First letter ____________capitalized –Second letter ______________capitalized New elements have three letter symbols __________________ to them Some elements originally had ___________ Example – Mercury, or hydragyras (Hg)

Identifying Elements – Names, Symbols, and Atomic Numbers Give either the name or the symbol of each (you may need to use Table S to do this!) NameSymbolNameSymbol NickelNiMagnesiumMg TungstenWRadiumRa RadonRnUraniumU BromineBrArsenicAs

Identifying Elements – Names, Symbols, and Atomic Numbers Atomic number - this represents the number of ____________ in the atom’s ______________ Each element has its own atomic number Therefore, the _______________ gives you the element Examples: Atomic number = 2 = 2 protons = _______ Atomic number = 8 = 8 protons = _______ Atomic number = 79 = 79 protons = _____

Identifying Elements – Names, Symbols, and Atomic Numbers Give the name of the element based on the atomic number (use Table S and the Periodic Table) Atomic # NameAtomic # Name 4Beryllium25Manganese 8Oxygen50Tin 12Magnesium75Rhenium 16Sulfur100Fermium

Identifying Elements – Names, Symbols, and Atomic Numbers The Atomic Number also gives us the number of electrons in an atom Remember, –Protons = charge of _____ –Electrons = charge of ______ –Neutrons = charge of ___________ –ATOMS are always electrically ___________ (charge = 0) –Therefore, in an atom, the # of __________= the # of ___________ but not the number of neutrons (that changes!)

Masses and Isotopes AS Aim #6: What makes something an isotope?

Using the Periodic Table to find Names, Symbols, and Atomic Numbers The Periodic Table of the elements is the master chart of chemistry Contains various pieces of information including: Atomic mass Oxidation (Total protons+neutrons) states Atomic Number Symbol (number of protons, only) Electron Configuration (arrangement of electrons in energy levels) C

Using the Periodic Table to find Names, Symbols, and Atomic Numbers Determine the following information for each element from the Periodic Table: NameSymbol Atomic Number Atomic Mass Electron Config HydrogenH BoronB ChlorineCl ArgonAr CalciumCa

Isotopes, Mass Numbers, and Neutrons Mass number – a measure of the number of ____________________________ in an atom Why not electrons too? _________________________!!! Masses of subatomic particles are measured in units called _____________________ or amu’s –Mass of 1 neutron = 1 amu –Mass of 1 proton = 1 amu –Mass of 1 electron = amu Therefore, Mass number = # of protons + # of neutrons

Isotopes, Mass Numbers, and Neutrons Does this mean that atoms of the same element all have the same mass numbers? ________! Atoms of the same element are actually a bit different We call them ISOTOPES –All atoms of an element have the ___________________ (# of protons) –But atoms of the same element can have ____________________ (different #s of neutrons)

Isotopes, Mass Numbers, and Neutrons Examples of Isotopes - hydrogen –There are three forms of hydrogen isotope Form of Hydrogen Isotope Atomic Number (# of protons) Mass Number (# of protons + neutrons) # of Neutrons Protium110 Deuterium121 Tritium132

Neutrons, Isotopes, and Mass Numbers Isotopes of hydrogen

Isotopes, Mass Numbers, and Neutrons Question 1 - an atom has an atomic number of 6, and a mass number of 12 amu. –What element is it? ______________ –How many protons does it have? ______________ –How many neutrons does it have? mass of 12 – 6 protons = 6 neutrons –How many electrons does it have? ________________________________ –IMPORTANT! 1 amu = 1/12 the mass of a typical carbon atom

Isotopes, Mass Numbers, and Neutrons Question 2 - an atom has an atomic number of 6, and a mass number of 14 amu. –What element is it? ____________ –How many protons does it have? ____________ –How many neutrons does it have? _______________________________ –How many electrons does it have? _______________________________ –This is an ISOTOPE of carbon

Neutrons, Isotopes, and Mass Numbers Isotopes of carbon

Representing isotopes Isotopes can be represented in several ways As the element with it _______________ –Ex: carbon-12, carbon-13, carbon-14 As the element’s symbol with its ________________ –Ex: C-12, C-13, C-14 As the symbol with both the __________ and the atomic number represented

Neutrons, Isotopes, and Mass Numbers Problem – how many protons, neutrons, and electrons are contained in a neutral atom of uranium-238, if the atomic number of uranium is 92? Mass number 238 = _______ Protons 92 = _______ Electrons 92 = ___ = ___ Neutrons 146 = _____________ - _____________

Average Atomic Masses AS Aim #7: Why do atomic mass numbers contain decimals?

Calculating Grade Averages You are in the class from H… the teacher has decided that your grade for the quarter will be based on the following weighting: –Exams60% –Homeworks30% –Labs10% You score 50% average on your exams, a 70% average on your homework, and an 90% average on your labs. Do you pass the course the first quarter?

Calculating Grade Averages If the teacher averaged the 3 grades, you would simply add your 3 grades and divide by 3 ( ) / 3 = ___________ = you pass and your family is happy! BUT = the grade is weighted, so: –Exams60% x 50% avg = –Homeworks30% x 70% avg = –Labs10% x 100% avg = ____ –The total comes out to be You fail, and now you get to attend extra help FOREVER

Calculating Grade Averages Problem #1 - Evil Mr. Foley decides your second quarter exams will be 80% of your Test grade, HW will be 10%, and Labs will be 10%. If you score a 60 avg on exams, an 80 avg on labs, and a 100 avg on labs, do you pass?

Calculating Grade Averages Problem #2 – Mr. Foley’s good twin decides in his class that the weighting will be quite different. For the second quarter, exams will be 50% of your grade, HW will be 30%, and Labs will be 20%. If you still score a 60 avg on exams, an 80 avg on homework, and a 100 avg on labs, do you pass?

Calculating Atomic Weights Determining the atomic weights of elements is the same _______________________________________ So we need to calculate the atomic weight based _______________________________ Example 1 – a sample of hydrogen isotopes: –Hydrogen-1 has an abundance of 95% –Hydrogen-2 has an abundance of 3% –Hydrogen-3 has an abundance of 2% What is the average atomic mass of this sample?

Calculating Atomic Weights Hydrogen-1 has an abundance of 95% Hydrogen-2 has an abundance of 3% Hydrogen-3 has an abundance of 2% Hydrogen 1 = 1 amu x 95% = Hydrogen 2 = 2 amu x 3% = Hydrogen 3 = 3 amu x 2% = ______

Calculating Atomic Weights Example 2: A sample of sulfur has the following isotopes in it –Sulfur-30 with an abundance of 60% –Sulfur-32 with an abundance of 30% –Sulfur-34 with an abundance of 10% What is the average atomic mass of this sulfur sample? Sulfur-30 = 30 amu x 60% = Sulfur-32 = 32 amu x 30% = Sulfur-34 = 34 amu x 10% = ________