Atomic Structure Ch. 5.1 & 5.2. Gotta start somewhere Let’s go backward in order to go forward...
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Transcript of Atomic Structure Ch. 5.1 & 5.2. Gotta start somewhere Let’s go backward in order to go forward...
Gotta start Gotta start somewheresomewhereLe t ’
s go backward in order to go forward
What was that all about?
• To study atoms and their interactions, we need to revisit something we studied earlier this year
•Matter and mass
So matter is made So matter is made of… of…
ELEMENTS!ELEMENTS!
Pure substancesPure substances that that cannot be broken down cannot be broken down chemically into simpler chemically into simpler kinds of matter kinds of matter
More than 100 elements More than 100 elements (92 naturally occurring)(92 naturally occurring)
AboutAbout 2525 of the 92 of the 92 natural elements are natural elements are essential to lifeessential to life
So matter is made So matter is made of… of…
ELEMENTS!
Pure substances that cannot be broken down chemically into simpler matter
More than 100 elements (92 naturally occurring)
About 25 of the 92 natural elements are essential to life
What about the rest of What about the rest of them?them?
Many used for new technology
Platinum: Catalytic converters, fuel cells, electrodes
Indium: Solar panels
Gallium: LED’s, laser diodes, photodetectors
Tantalum: Microchips, new technologies
ATOMSATOMSThe simplest particle of an element that retains all the properties of that element
Atoms of each element Atoms of each element of have unique of have unique properties that properties that determine how that determine how that element behaves during element behaves during chemical reactionschemical reactions
What do we know about What do we know about ATOMS?ATOMS?
Dalton’s Atomic Theory Dalton’s Atomic Theory summarizes the key ideassummarizes the key ideas
1. All elements are composed 1. All elements are composed of tiny indivisible particles of tiny indivisible particles called atoms*called atoms*
2. Atoms of the same element 2. Atoms of the same element are identical. Each element is are identical. Each element is made of one type of atom.made of one type of atom.
What do we know about What do we know about ATOMS?ATOMS?
Dalton’s Atomic Theory summarizes the key ideas
3. Atoms of different elements can mix together physically or chemically combine to make compounds
4. Chemical reactions occur when atoms are separated, joined or rearranged. Atoms of one element are never changed into atoms of another element.
How big How big (or small) (or small) is an is an atom?atom?
Cell Size and Scale – University of Utah Genetics
If a penny was made of pure copper, there would be approximately 2.4x1022 atoms in that one coin.
100 million copper atoms lined up in a row would cover 1 cm of distance
How big How big (or small) (or small) is an is an atom?atom?
A typical human hair is approximately 1 million carbon atoms wide
100x magnification 400x magnification
Is it possible to Is it possible to see atoms?see atoms?
Yes, with very advanced microscopesYes, with very advanced microscopes
STM – Scanning Tunneling MicroscopeSTM – Scanning Tunneling Microscope
Pb atoms on silicon surface
““The STM works by scanning a very sharp The STM works by scanning a very sharp metal wire tip over a surface. By bringing metal wire tip over a surface. By bringing the tip very close to the surface, and by the tip very close to the surface, and by applying an electrical voltage to the tip or applying an electrical voltage to the tip or sample, we can image the surface at an sample, we can image the surface at an extremely small scale – down to resolving extremely small scale – down to resolving individual atoms.” individual atoms.” Nanoscienceinstruments.comNanoscienceinstruments.com
Atomic StructureAtomic StructureThree particles make up atomsThree particles make up atoms
Protons - Mass of 1 amu, Charge of +1Protons - Mass of 1 amu, Charge of +1
Neutrons – Mass of 1 amu, No charge Neutrons – Mass of 1 amu, No charge (neutral)(neutral)
Electrons – No mass, Charge of -1Electrons – No mass, Charge of -1
Atomic StructureAtomic StructureThree particles make up atomsThree particles make up atoms
Protons - Mass of 1 amu, Charge of +1Protons - Mass of 1 amu, Charge of +1
Neutrons – Mass of 1 amu, No charge (neutral)Neutrons – Mass of 1 amu, No charge (neutral)
Electrons – No mass, Charge of -1Electrons – No mass, Charge of -1
Atoms have two regions: Atoms have two regions: The nucleusThe nucleus in in the center, and the center, and The outer energy levelsThe outer energy levels
Protons and Neutrons are found in the Protons and Neutrons are found in the nucleus, Electrons are found in the nucleus, Electrons are found in the outer energy levelsouter energy levels
Atomic Structure Atomic Structure Subatomic Particles
Protons Neutrons Electrons
Location Nucleus Nucleus Electron Cloud (energy levels)
Charge + (positive) 0, neutral -, negative
Mass Appx 1.7X10-24 grams or 1amu
Appx 1.9 X10-24 grams or 1 amu
0
How to determine the number in each atom
Atomic # Atomic Mass-Atomic #
Same as # of Protons if atom has no charge
Special Fxn Gives Atoms their identity
Different #s within the same type of atom creates isotopes
Determine chemical reactivity
Atom TerminologyAtom Terminology
The The Atomic Number Atomic Number for an element for an element is the number of protons in an atom of is the number of protons in an atom of that element. that element.
Hydrogen atoms all have one proton, Hydrogen atoms all have one proton, so the Atomic Number for Hydrogen is so the Atomic Number for Hydrogen is 11
Atoms with different atomic numbers Atoms with different atomic numbers will be from different elementswill be from different elements
Atom TerminologyAtom TerminologyMass number is the total Mass number is the total number of protons and number of protons and neutrons in an atomneutrons in an atom
# of neutrons = mass number # of neutrons = mass number – # of protons (atomic – # of protons (atomic number)number)
Terminology ContinuedTerminology ContinuedIsotopes: Atoms of the same element that have different numbers of neutrons
IsotopesIsotopesAtoms
Atoms of the same element that vary in the number of ___________
(atomic # same, atomic mass varies)
neutrons
IsotopesIsotopes1
H
1
2
H
1
3
H
1
Potassium in a banana: 39K (93.25%), 40K (6.7302%) and 41K (0.0117%)
Atomic # 19
99.98% 0.015% trace
19p 20n 19e
19p 21n 19e 19p 22n 19e
Why do atomic masses Why do atomic masses (mass #) have decimal (mass #) have decimal
places?places?Most elements exist as mixtures of Most elements exist as mixtures of two or more isotopes. two or more isotopes.
Atomic mass Atomic mass is the average mass is the average mass of all of the isotopes of given of all of the isotopes of given element.element.
Determine the Mass # of Determine the Mass # of Carbon Carbon
C-12 98.89%
C-13 1.11%
C-14 trace
12.011C6
12 x .9889 = 11.8668
13 x .0111= 0.1443
+
12.0111
The ElectronsThe ElectronsTravel at very high speedsTravel at very high speeds at various at various distances distances (energy levels)(energy levels) from the nucleus from the nucleus
Electrons in the same energy level are Electrons in the same energy level are approximately the same distance from the approximately the same distance from the nucleusnucleus
Outer energy levels have more energy than Outer energy levels have more energy than inner levelsinner levels
Each levelEach level holds only a holds only a certain number of certain number of electronselectrons
Remember 2 8 8 !
Subatomic ParticlesSubatomic Particles
ProtonsProtons
NeutronsNeutrons
ElectronsElectrons
Drawing AtomsDrawing Atoms
Atomic # Atomic #
Atomic MassAtomic Mass
(Mass #)(Mass #)19
F
9
1
H
1
12C
6
Atoms1P0N
1e
9P10N 2
e 7e
6P6N 2
e4e
Periodic TablePeriodic Table1 2
3 4 5 6
•Elements arranged on a periodic table by their atomic numbers
7 8
Periodic Periodic TableTable
Period Tells the number of energy levels
Fam
ily Tells the number of outermost electrons
# of outermost electrons
CompoundsCompoundsMost elements do not exist Most elements do not exist by themselvesby themselves
Readily combine with other Readily combine with other elementselements in a predictable in a predictable fashionfashion
CompoundCompound Pure substance Pure substance made up made up of atoms of two or more of atoms of two or more elementselementsProportion of atoms are Proportion of atoms are always fixedalways fixedIonic or covalently bondedIonic or covalently bonded
Chemical formulaChemical formula: the : the kindkind and and proportion proportion of atoms of of atoms of each element in a compound each element in a compound
EX: HEX: H22OO H2O
Molecules: two or more elements covalently bonded (the elements can be the same (O2) or different (CO2)
SAME!
Let’s welcome our friend…
GLUCOSE!
Atoms of different elements
Blue: CarbonRed: OxygenGray: Hydrogen
MoleculeMolecule
The simplest part of a The simplest part of a substance that retains all of substance that retains all of the properties of the the properties of the substance and exists in a free substance and exists in a free statestate
Some can be very Some can be very LARGELARGE and and COMPLEXCOMPLEX
Key Difference Between Key Difference Between Molecules and CompoundsMolecules and Compounds
Compounds: Made of two or more Compounds: Made of two or more different types of atomsdifferent types of atoms
Molecules: Made of the same or Molecules: Made of the same or different types of atomsdifferent types of atoms
Chemical FormulasChemical Formulas 6CO2 + 6H2O C6H12O6 + 6O2When have we seen this before?What are the pieces?What exactly is this formula telling us?
Chemical equationsChemical equations represent represent chemical reactionschemical reactions
A ____________ represents the A ____________ represents the number of number of moleculesmolecules involved in involved in the reactionthe reaction
A _____________represents the A _____________represents the number of number of atomsatoms in each molecule in each molecule
coefficient
subscript2H2O
2H2O
Chemical FormulasChemical Formulas 6CO2 + 6H2O C6H12O6 + 6O2
How many atoms of carbon are in a molecule of glucose? (subscript)
How many water molecules are necessary to make a molecule of glucose? (coefficient)
6
6
Chemical equationsChemical equations represent represent chemical reactionschemical reactions
Chemical ReactionsChemical Reactions: Atoms in an existing : Atoms in an existing substance are substance are rearrangedrearranged to form a new to form a new substance. substance.
Chemical bonds in the reactants are Chemical bonds in the reactants are brokenbroken, and , and new bonds are new bonds are formedformed to make the products. to make the products.
A A Chemical EquationChemical Equation represents the chemical represents the chemical reaction that converts the original substances reaction that converts the original substances (original forms of matter) into new substances (original forms of matter) into new substances (new forms of matter)(new forms of matter)
22HH22 + 0 + 02222HH22OOReactants
Products
Chemical equationsChemical equations represent represent chemical reactionschemical reactions
A A Chemical EquationChemical Equation represents the represents the chemical reaction that converts the chemical reaction that converts the original substances (original forms of original substances (original forms of matter) into new substances (new matter) into new substances (new forms of matter)forms of matter)
Reactants
Products 6CO2 + 6H2O C6H12O6 + 6O2
• The number of each kind of atom must be the same in both the reactants and products
An attraction between An attraction between atoms that forms as a atoms that forms as a result of the sharing or result of the sharing or complete transfer of complete transfer of electrons.electrons.
Atoms tend to reactAtoms tend to react (combine) with other (combine) with other atoms atoms in order to become in order to become more stablemore stable (undergo (undergo chemical reactions)chemical reactions)
Stability = full outer electron Stability = full outer electron levellevel
Chemical Bonds
What about the What about the family farthest to family farthest to
the right?the right?The noble gases have a full outer electron shell and thus do not want to react with other elements.
They are stable!
Ionic BondsIonic BondsSome atoms become stable by Some atoms become stable by becoming ions--- becoming ions--- losing or gaining losing or gaining electronselectrons
Atoms that Atoms that lose electronslose electrons are called are called positive ions _____________positive ions _____________
Atoms thatAtoms that gain electrons gain electrons are calledare called negative ions __________negative ions __________
cations
anions
Because Because positive and negative positive and negative electrical charges attractelectrical charges attract each other each other
ionic bondsionic bonds form form
Other ionic compounds: CaCl2 KBr
MgF2
The The physical and physical and chemical propertieschemical properties of a of a compound differ from compound differ from the physical and the physical and chemical properties of chemical properties of the individual elements the individual elements that compose itthat compose it
Sodium- soft, silvery white, highly reactive metal
Will Kill You
Chlorine- yellowish green , non metal, gas
Will Kill You
Sodium Chloride-
Table Salt
YUM
Example of emergent properties
Emergent property: Characteristic of a system not observed in any of its individual components.
Other example
Covalent BondsCovalent BondsFormed when two Formed when two atoms atoms share one or share one or more pairs of more pairs of electronselectrons
Octet RuleOctet Rule
Covalent v. Ionic Covalent v. Ionic BondsBondsCovalent Ionic
Inter-element interaction
Sharing of electrons to make full outer electron shells
Transfer of electrons to make full outer electron shells
Reason for happening
Increased stability
Increased stability
Attraction is the result of
Dependence on other atom for electron sharing
+/- charges of ions
Typical Example
NaCl H2O
Bonds make Compounds or molecules
Compounds