Presentation on theme: "Chapter #3 Atoms: The Building Blocks of Matter Chapter #3 ATOMS:"— Presentation transcript:
1 Chapter #3 Atoms: The Building Blocks of Matter Chapter #3 ATOMS:
2 3-1 Early Atomic TheoryDo Not need in notesAtoms are so small they cannot be observed directly. Scientists could use only experimental data to help describe the atom.Around 400 B.C., Democritus (a Greek philosopher) suggested that the world was made of two things - empty space and tiny particles called atoms.During the 1800's, a French Chemist (Antoine Lavoisier) discovered that chemical "changes" occurring in a closed system - the mass after a chemical change equaled the mass before the chemical change.He proposed that, in ordinary chemical reactions, matter can be changed in many ways, but it cannot be created or destroyed (Law of Conservation of Mass).Work by another French Chemist, Joseph Proust, had observed that specific substances always contain elements in the same ratio by mass (Law of Definite Proportions.)
3 Foundations of Atomic Theory Law of Definite Proportions: The elements composing a compound are always found in the same ratio by mass.Law of Multiple Proportions: The masses of one element that combine with a fixed amount of another element to form more than one compound are in the ratio of small whole numbers. Example CO, CO2
4 Dalton was the founder of Atomic Theory. For example: Oxygen can combine with Carbon to form Carbon Monoxide, CO, or form Carbon Dioxide, CO2.CompoundMass of C in SampleMass of O in SampleRatio of O masses combined with constant massCarbon Monoxide, CO12 g16 g1:1Carbon Dioxide, CO212g32 g2:1Dalton was the founder of Atomic Theory.
5 Dalton’s Atomic Theory All matter is composed of extremely small particles called atoms.Atoms of a given element are identical in size, mass and other properties; atoms of different elements differ in size, mass, and other properties.Atoms cannot be subdivided, created, or destroyed.Atoms of different elements combine in simple whole-number ratios to form chemical compounds.In chemical reactions, atoms are combined, separated, or rearranged.
6 Modern Atomic TheoryElement have a characteristic average mass which is unique to that element.Atoms cannot be subdivided, created, or destroyed in ordinary chemical reactions. However, these changes CAN occur in nuclear reactions!All matter is composed of atomsAtoms of any one element differ in properties from atoms of another element
7 Section 3-2Atom- the smallest particle of an element that retains the chemical properties of that element.Nucleus- is the positively charges, dense central portion of the atom that contains nearly all of its mass but takes up only an insignificant fraction of its volume.
8 Subatomic Particles Electrons e- Negatively charged particles found around the nucleus in shells, energy level or electron cloudsProtonsp+Positively charged particles. Found in the nucleusNeutronsNNo charge. Found in the nucleus.
9 The Atomic ScaleMost of the mass of the atom is in the nucleus (protons and neutrons)Electrons are found outside of the nucleus (the electron cloud) e- have very tiny mass.Most of the volume of the atom is empty space
10 Drawing atoms In the nucleus Symbol # of p+ # of N Outside the nucleus in the energy shells/levelelectrons
11 Famous Scientist Scientist Experiment Name What it proved JJ Thomson Cathode RayElectrons have a negative chareRobert MillikanOil DropMass of an electronErnest RutherfordMetal Foil or gold foilNucleus contains positive charge
12 Discovery of the Electron Do NOT need in NotesDiscovery of the ElectronIn 1897, J.J. Thomson used a cathode ray tube to deduce the presence of a negatively charged particle.Cathode ray tubes pass electricity through a gas that is contained at a very low pressure.
13 Thomson was awarded the Nobel Prize in 1906 for his "discovery" of the first sub-atomic particle; the electron. This discovery strongly implied that Dalton was wrong and that the atom was not the smallest particle of matter. It looked as if the atom could be broken down into even smaller pieces, and to Thomson these smaller pieces were his negatively charged electrons.Do NOT need in NOTES
14 Conclusions from the Study of the Electron Do NOT need in NOTESConclusions from the Study of the ElectronCathode rays have identical properties regardless of the element used to produce them. All elements must contain identically charged electrons.Atoms are neutral, so there must be positive particles in the atom to balance the negative charge of the electronsElectrons have so little mass that atoms must contain other particles that account for most of the mass
15 Thomson’s Atomic Model Do NOT need in NOTESThomson’s Atomic ModelThomson believed that the electrons were like plums embedded in a positively charged “pudding,” thus it was called the “plum pudding” model.
16 Rutherford’s Gold Foil Experiment Do NOT need in NOTESRutherford’s Gold Foil ExperimentAlpha particles are helium nucleiParticles were fired at a thin sheet of gold foilParticle hits on the detecting screen (film) are recorded
17 Rutherford’s Findings DO NOT Need in NotesRutherford’s FindingsMost of the particles passed right throughA few particles were deflectedVERY FEW were greatly deflectedConclusions:The nucleus is smallThe nucleus is denseThe nucleus is positively charged
18 Section 3-3Atomic number (Z) of an element is the number of protons in the nucleus of each atom of that element.The number of protons = the number of electrons6CCarbon12.011
19 Mass NumberMass number is the number of protons and neutrons in the nucleus of an isotope.Mass # = p+ + nSOooo the number of Neutrons =n= Mass # - p+
20 Isotopes Mass # Atomic # Symbol Isotopes are atoms of the same element that have different masses. (number of neutrons)Mass #Atomic # Symbol
21 235 92 Nuclear Symbols Mass number (p+ + n) Mass number (p+ + n) Element symbolAtomic number (# of p+)U23592
22 Hyphen Notation Sodium-23 (23 is the mass #) Sooo… (atomic #) = 12 for the # of neutrons.11 is the # of protons and electrons.
23 Isotopes of H p+ e- n 1 2 Isotopes Hydrogen–1 (protium) Hydrogen-2 Hydrogen-2(deuterium)Hydrogen-3(tritium)2
24 The Mole 1 dozen =12 1 gross = 144 1 ream = 500 1 mole = 6.022 x 1023 There are exactly 12 grams of carbon-12 in one mole of carbon-12.
25 Calculations: Converting moles to grams Given # of mole X ? g (look at periodic table)= g of1 moleHow many grams of lithium are in 3.50 moles of lithium?3.50 mole X g = g Li1 mol
26 Calculations: Converting grams to moles Given # of g X 1 mol = mol ofg (look at periodic table)How many moles of lithium are in 18.2 grams of lithium?18.2 g X 1 mol Li = mol Li6.941 g
27 I didn’t discover it. Its just named after me! Avogadro’s NumberIs the number of particles in exactly one mole of a pure substance.6.022 x 1023 is called “Avogadro’s Number” in honor of the Italian chemist Amadeo Avogadro ( ).I didn’t discover it. Its just named after me!
28 Calculations: Converting Moles to Particles Given # of mol x x 1023 part= atoms1 molHow many atoms/particles/molecules of lithium are in 3.50 moles of lithium?3.50 mole X x = x 1024 atoms of Li
29 Calculations: Converting Particles to Moles Given # of particles x 1 mole = mol6.022 x 1023How many moles of lithium are there in x particles of Li?x 1024 part x 1 mole = mol Li6.022 x 1023 part
30 Calculations: Converting grams to particles Given # of grams x 1 mol x x 1023= particles? g molHow many atoms/particles/molecules of lithium are in 18.2 g of lithium?18.2 g x 1 mol x x 1023 = x 1024 particle Li6.941g mol
31 Calculations: Converting particles to grams Given # of particles x 1 mol x ? g = g6.022 x molHow many grams are there in 8.02 x 1025 particles of lithium?
32 Work Cited“JJ Thomson”. Photo. July 28,Cathode Ray Image and JJ Thomson Model. Image. July 28,“Gold Foil Experiment”. Image. July 28,“Rutherford”. Photo. July 28,“Mole”. Photo. Aug 8,
33 “Hydrogen Isotopes”. Picture. August 4, 2006. www. sr. bham. ac “Hydrogen Isotopes”. Picture. August 4,“Amedeo Avogadro”. avagadroc.jpg August 4, poohbah.cem.msu.edu/Portraits/PortraitsH...“Uranium symbol”. Picture. August 4, webelements/scholar/...Holt, Rinehart and Winston. Modern Chemistry. Harcourt Brace & Company“Atom Comic Cover”. Photo. Aug. 12,