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ADDITIONAL RESOURCESADDITIONAL RESOURCES
AtomAtom
Isaac AsimovIsaac Asimov
ISBN:0613033884 ISBN:0613033884
Any chemistry by Asimov is goodAny chemistry by Asimov is good
WARNINGWARNING
The material from this point on may The material from this point on may start out sounding like high school start out sounding like high school chemistrychemistry
The high school sounding material is The high school sounding material is like a runway, we use it to take off like a runway, we use it to take off fromfrom
Don’t get board or over-confident Don’t get board or over-confident with the runway, or you WILL miss with the runway, or you WILL miss the flightthe flight
ATOMIC THEORYATOMIC THEORY
Has been around for over 2,000 years, Has been around for over 2,000 years, the word ATOM is from the Greek word the word ATOM is from the Greek word atomosatomos meaning uncuttable meaning uncuttable
In the early 1800s, atomic theory was In the early 1800s, atomic theory was dusted off and formed the basis of dusted off and formed the basis of modern chemistrymodern chemistry
From here forward, we are talking about From here forward, we are talking about the 1800s flavor of atomic theorythe 1800s flavor of atomic theory
ATOMIC THEORYATOMIC THEORYFour “postulates” (rules):Four “postulates” (rules):
1.1. Each element is composed of very small Each element is composed of very small particles called atomsparticles called atoms
2.2. Atoms of a given element are identical to Atoms of a given element are identical to each other in mass and properties, but each other in mass and properties, but are different from atoms of other are different from atoms of other elementselements
3.3. Atoms of one element can not be Atoms of one element can not be changed into atoms of a different changed into atoms of a different elementelement
4.4. Compounds are formed when atoms of Compounds are formed when atoms of two or more elements combinetwo or more elements combine
ATOMIC THEORYATOMIC THEORY
Explained two laws:Explained two laws:1.1. Constant Composition – Compounds Constant Composition – Compounds
always have the same ratio of always have the same ratio of elementselements
2.2. Conservation of Matter – The total Conservation of Matter – The total mass of material mass of material afterafter a a chemical chemical reactionreaction is the same as the total mass is the same as the total mass beforebefore the reaction (this is the basis for the reaction (this is the basis for everything that will follow in this class)everything that will follow in this class)
ATOMIC THEORYATOMIC THEORYA new law was discovered at this time, A new law was discovered at this time,
the Law of Multiple Proportions:the Law of Multiple Proportions:
If two elements A and B combine to If two elements A and B combine to form more the one compounds, the form more the one compounds, the ratio A to B will be different for each ratio A to B will be different for each compound.compound.
NONO22, NO, NO3 3 (NOx, they cause smog)(NOx, they cause smog)
SOSO22, SO, SO3 3 (SOx,(SOx, they cause acid rain)they cause acid rain)
ATOMIC STRUCTUREATOMIC STRUCTURE
Please forget the “Pool Ball” “Planets Please forget the “Pool Ball” “Planets Around the Sun” image of electronsAround the Sun” image of electrons
Electrons act very strangely Electrons act very strangely For accounting purposes, if we need For accounting purposes, if we need
to, electrons will be drawn as dots or to, electrons will be drawn as dots or minus signs next to the atomic minus signs next to the atomic symbol symbol
ATOMIC STRUCTUREATOMIC STRUCTURE
Read the text book if you want a Read the text book if you want a pitch – by – pitch description of who pitch – by – pitch description of who did what when (this is chemistry, not did what when (this is chemistry, not history)history)
Atoms have two regions – the Atoms have two regions – the nucleus and the electron cloudnucleus and the electron cloud
If this dot If this dot ●● were a nucleus, the were a nucleus, the electron cloud would be on the third electron cloud would be on the third floorfloor
ATOMIC STRUCTUREATOMIC STRUCTURETHE NUCLEUSTHE NUCLEUS
Two particles in the nucleus:Two particles in the nucleus:
ProtonsProtons
NeutronsNeutrons
ATOMIC STRUCTUREATOMIC STRUCTURETHE NUCLEUSTHE NUCLEUS
ProtonsProtons Have an atomic mass of just Have an atomic mass of just
under 1under 1 Have a charge of +1Have a charge of +1 Do not participate in chemical Do not participate in chemical
reactionsreactions Determine what element the Determine what element the
atom isatom is
ATOMIC STRUCTUREATOMIC STRUCTURETHE NUCLEUSTHE NUCLEUS
ProtonsProtons 1 proton is Hydrogen1 proton is Hydrogen 8 protons Oxygen8 protons Oxygen 92 protons is Uranium92 protons is Uranium
ProtonsProtons
We call the NUMBER of We call the NUMBER of protons in an atom the protons in an atom the ATOMIC NUMBER since it ATOMIC NUMBER since it determines what element determines what element it isit is
ATOMIC STRUCTUREATOMIC STRUCTURETHE NUCLEUSTHE NUCLEUS
NeutronsNeutrons Have an atomic mass of 1Have an atomic mass of 1 Have a charge of 0Have a charge of 0 Do not participate in chemical Do not participate in chemical
reactionsreactions Atoms of the same element can Atoms of the same element can
have DIFFERENT numbers of have DIFFERENT numbers of neutronsneutrons
ATOMIC STRUCTUREATOMIC STRUCTURETHE NUCLEUSTHE NUCLEUS
NeutronsNeutrons Atoms of the same element with Atoms of the same element with
different numbers of neutrons are different numbers of neutrons are call isotopescall isotopes
Isotopes of an element have different Isotopes of an element have different weights, but they have identical weights, but they have identical chemical properties (which is why it’s chemical properties (which is why it’s so hard to separate them)so hard to separate them)
ATOMIC STRUCTUREATOMIC STRUCTURETHE NUCLEUSTHE NUCLEUS
If an atom of carbon (atomic number If an atom of carbon (atomic number 6) has 12 neutrons what is it’s atomic 6) has 12 neutrons what is it’s atomic weight?weight?
6 protons (weight ≈1)6 protons (weight ≈1)12 neutrons12 neutrons (weight = 1) (weight = 1) 18 AMUs (Atomic Mass Units)18 AMUs (Atomic Mass Units)
Carbon has an isotope with 14 neutrons Carbon has an isotope with 14 neutrons it’s weight is 20 AMUsit’s weight is 20 AMUs
1 AMU = 1.66054 * 101 AMU = 1.66054 * 10-24-24 grams grams
ATOMIC STRUCTUREATOMIC STRUCTURETHE NUCLEUSTHE NUCLEUS
On the periodic table, carbon weight is On the periodic table, carbon weight is listed as 12.0107, the extra 0.0107 is listed as 12.0107, the extra 0.0107 is from the carbon 14. What fraction of from the carbon 14. What fraction of carbon is C14?carbon is C14?
X*12+y*14 = 12.0107 x+y=1X*12+y*14 = 12.0107 x+y=1
(1-y)12+14y=12.0107 x=1-y(1-y)12+14y=12.0107 x=1-y
12-12y+14y=12.010712-12y+14y=12.0107
2y=0.0107, y=0.0054 or 54 of 10,0002y=0.0107, y=0.0054 or 54 of 10,000
ATOMIC STRUCTUREATOMIC STRUCTURETHE NUCLEUSTHE NUCLEUS
NomenclatureNomenclature To write atomic isotopesTo write atomic isotopes
1.1. Write the atomic symbol Write the atomic symbol CC
2.2. Write the mass number as a Write the mass number as a superscript to the LEFT of the symbol superscript to the LEFT of the symbol 1212CC or or 1414CC
3.3. There is no need to write the atomic There is no need to write the atomic number since it is constant for the number since it is constant for the element (carbon is 6)element (carbon is 6)
ATOMIC STRUCTUREATOMIC STRUCTURETHE NUCLEUSTHE NUCLEUS
Don’t think of electrons as moons Don’t think of electrons as moons orbiting a planetorbiting a planet
Think of them as making concentric Think of them as making concentric shells around the nucleusshells around the nucleus
ATOMIC STRUCTUREATOMIC STRUCTURETHE ELECTRON CLOUDTHE ELECTRON CLOUD
Electrons are most probably in the Electrons are most probably in the shellshell
Each shell level has a certain number Each shell level has a certain number of electrons it can hold (remember of electrons it can hold (remember this in a few slides when we get to this in a few slides when we get to the periodic table)the periodic table)
How electrons behave in these shells How electrons behave in these shells determine the elements chemical determine the elements chemical and sometimes physical propertiesand sometimes physical properties
ATOMIC STRUCTUREATOMIC STRUCTURETHE ELECTRON CLOUDTHE ELECTRON CLOUD
THE PERIODIC TABLETHE PERIODIC TABLE
Some elements have very similar Some elements have very similar chemical propertieschemical properties
When Nobel listed the elements in When Nobel listed the elements in increasing order of atomic number, increasing order of atomic number, he noticed that the every so often, he noticed that the every so often, he came to a non-reactive gas that he came to a non-reactive gas that was followed by a soft, reactive was followed by a soft, reactive metalmetal
He also noticed that the elements in He also noticed that the elements in between also repeated in a patternbetween also repeated in a pattern
So he arranged the elements with similar So he arranged the elements with similar properties in groups.properties in groups.
He listed the groups as columns going He listed the groups as columns going from light on top to heavy on the bottomfrom light on top to heavy on the bottom
The groups were arranged next to each The groups were arranged next to each other left to right by increasing atomic other left to right by increasing atomic number of the first elementnumber of the first element
THE PERIODIC TABLETHE PERIODIC TABLE
THE PERIODIC TABLETHE PERIODIC TABLE
Columns are called Columns are called GroupsGroups and have and have similar propertiessimilar properties
Rows are called Rows are called FamiliesFamilies and are and are filling the same “levels” of electron filling the same “levels” of electron shellsshells
THE PERIODIC TABLETHE PERIODIC TABLE
Some GroupsSome GroupsAlkaliAlkali RareRare HalogensHalogens
NobelNobel
EarthEarth Gasses Gasses MetalsMetals
How to read the tableHow to read the table
Atomic NumberAtomic NumberAtomic SymbolAtomic SymbolAtomic WeightAtomic Weight
Some fancy tables will also have the Some fancy tables will also have the electron configuration on the bottom.electron configuration on the bottom.
THE PERIODIC TABLETHE PERIODIC TABLE
47
Ag107.868
2
MOLECULESMOLECULES
Diatomic MoleculesDiatomic Molecules Are made of two atoms of the same Are made of two atoms of the same
element Oelement O22, H, H22
Remember the name BrINClOHFRemember the name BrINClOHF• Br – BromineBr – Bromine ●I - Iodine●I - Iodine• N – NitrogenN – Nitrogen ●Cl – Chlorine●Cl – Chlorine• O – OxygenO – Oxygen ●H – Hydrogen●H – Hydrogen• F - FluorineF - Fluorine
Formulas - Three Main TypesFormulas - Three Main Types
1.1. Molecular – Types and actual Molecular – Types and actual number of atoms involved (Hnumber of atoms involved (H22O, O, CSCS22, MgCl, MgCl2 2 HH22OO22))
2.2. Empirical – Types and ratio of Empirical – Types and ratio of atoms involved (atoms involved (HOHO))
3.3. Structural – Types, amounts, & how Structural – Types, amounts, & how they are put togetherthey are put together
MOLECULESMOLECULES
Ions & Ionic CompoundsIons & Ionic Compounds All atoms want to have a full outer All atoms want to have a full outer
shell of electrons (either 2, 8, 10 or shell of electrons (either 2, 8, 10 or 14)14)
MOLECULESMOLECULES
Ions & Ionic CompoundsIons & Ionic Compounds On the periodic table, elements on On the periodic table, elements on
the left (metals) loose electrons and the left (metals) loose electrons and become positively charged. They are become positively charged. They are called called CATIONS (Plus cats)CATIONS (Plus cats)
Elements on the right gain electrons Elements on the right gain electrons and become negatively charged. and become negatively charged. They are called They are called ANIONS (minus ANIONS (minus onions)onions)
MOLECULESMOLECULES
Ions & Ionic CompoundsIons & Ionic Compounds ““Opposites attract” Paula Abdul 1986Opposites attract” Paula Abdul 1986 Ionic reactions happen when a metal Ionic reactions happen when a metal
looses electrons with a non-metal. looses electrons with a non-metal. The metal becomes positive, the The metal becomes positive, the
non-metal negative and form the non-metal negative and form the ionic compoundionic compound
Ionic compounds are usually soluble Ionic compounds are usually soluble in waterin water
MOLECULESMOLECULES
Ions & Ionic CompoundsIons & Ionic Compounds
Magnesium ChlorideMagnesium Chloride
MOLECULESMOLECULES
Mg-
Cl
-
-
-
-
-
-
-
-
Cl-
-
-
-
-
-
-
Ions & Ionic CompoundsIons & Ionic CompoundsMagnesium ChlorideMagnesium Chloride
MOLECULESMOLECULES
Mg +2-
Cl-1
-
-
-
-
-
-
-
-
Cl-1-
-
-
-
---
Ions & Ionic Compounds - Magnesium Ions & Ionic Compounds - Magnesium ChlorideChloride
We now have MgWe now have Mg+2+2 and 2Cl and 2Cl-1-1
We started with zero net charge, and We started with zero net charge, and we ended with zero net charge we ended with zero net charge ++2+2(2+2(--1) = 01) = 0
The formula is MgClThe formula is MgCl22
MOLECULESMOLECULES
Cross Method of Empirical FormulasCross Method of Empirical Formulas
MgMg+2+2 ClCl-1-1
MOLECULESMOLECULES
21
Full shells are happy shells!!!!Full shells are happy shells!!!!
Why don’t noble gasses participate Why don’t noble gasses participate in reactions?in reactions?
Anticipating Ionic ChargeAnticipating Ionic Charge Mg formed a +2 ion and is in the Mg formed a +2 ion and is in the
second family from the leftsecond family from the left Cl formed a -1 ion and is in the Cl formed a -1 ion and is in the
second family on the rightsecond family on the right The family all the way on the right The family all the way on the right
are the noble gasses. They are stuck are the noble gasses. They are stuck up and don’t count!up and don’t count!
MOLECULESMOLECULES
Anticipating Ionic ChargeAnticipating Ionic Charge Cations – If not in the center “short Cations – If not in the center “short
rows”, count from the left. That’s the rows”, count from the left. That’s the charge the element will usually formcharge the element will usually form
Anions – Skip the noble gas column Anions – Skip the noble gas column and count to the leftand count to the left
At 4, charges switch At 4, charges switch
MOLECULESMOLECULES
Anticipating Ionic ChargeAnticipating Ionic Charge Elements in the middle (transition Elements in the middle (transition
metals) form cations, but can vary in metals) form cations, but can vary in charge from 1 to 7charge from 1 to 7
MOLECULESMOLECULES
Elements on the immediate right of Elements on the immediate right of the transition metals are called the transition metals are called metalloids and usually do not form metalloids and usually do not form ions.ions.
MOLECULESMOLECULES
Covalent BondsCovalent Bonds Ionic bonds transfer electrons from Ionic bonds transfer electrons from
one atom to another setting up an one atom to another setting up an electrical attractionelectrical attraction
CovalentCovalent bonds occur when two bonds occur when two atoms atoms shareshare electrons electrons
At any given instant the electron At any given instant the electron could be with atom 1 or atom 2could be with atom 1 or atom 2
CovalentCovalent – Cumby a – Cumby a
MOLECULESMOLECULES
Covalent BondsCovalent Bonds Organic molecules use Organic molecules use covalentcovalent bonds bonds Carbon and silicone can both bond with Carbon and silicone can both bond with
itselfitself Chains of carbon atoms make organic Chains of carbon atoms make organic
moleculesmolecules
The magic number is The magic number is 4 4 each carbon each carbon forms 4 covalent bondsforms 4 covalent bonds
MOLECULESMOLECULES
Covalent Bonds – Alkanes – Single C – to- C BondsCovalent Bonds – Alkanes – Single C – to- C Bonds
MOLECULESMOLECULES
methane
ethane
propane
MOLECULESMOLECULES
Covalent Bonds – Alkenes – Double C – Covalent Bonds – Alkenes – Double C – to- C Bondsto- C Bonds
ethene
propene
Organic Molecules & the Covalent Organic Molecules & the Covalent BondBond
One final note – unlike ionic molecules, One final note – unlike ionic molecules, you can not anticipate how many you can not anticipate how many bonds will form just by position on bonds will form just by position on the tablethe table
MOLECULESMOLECULES