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Warm Up: Dimensional Analysis Practice. The relative mass of an electron is 0.000586 amu . a. Write in scientific notation If a proton has a relative mass of 1.007276 amu , how many electrons could fit on a proton? c . The actual mass of an electron is 9.109 x 10 -31 kg. Convert to mg.
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Warm Up:Dimensional Analysis Practice The relative mass of an electron is 0.000586 amu. a. Write in scientific notation • If a proton has a relative mass of 1.007276 amu, how many electrons could fit on a proton? c. The actual mass of an electron is 9.109 x 10-31kg. Convert to mg
Atomic Theory has Evolved! Why has the atomic theory changed through the years? Qualitative vs. Quantitative data
Law of Conservation of Mass Mass is neither created nor destroyed during an ordinary chemical reaction or physical change. Candle Lab: C25H52 + O2 + E CO2 + H2O + C + E
Draw a picture and explain why it happens? • Tear up a piece of paper. Rub the balloon against your clean, dry (product free) hair. Hold the balloon next to the paper. Make observations. • Rub the balloon against your hair. Hold the balloon close to running water. Make observations. • Explain to the best of your abilities what is happening.
Pioneers of the Atomic TheoryChapter 3 Observant people have been looking at matter and pondering why different phenomenon occur for hundreds of years.
Early Philosophers Didn’t agree!!
Dead Dude #1- Democritus Ancient philosopher- 460BC Matter is made of indivisible particles. Atomos means “that which cannot be further broken down”
Shortcomings It is a conceptual definition, not based on science. Doesn’t talk about subatomic particles.
Dead Dude#2- DaltonExplained the Laws • John Dalton (early 1800s) • Atom is a solid, indestructible mass (like a billiard ball)
All Atomic Theory builds on Dalton’s Law • All matter is made of tiny particles called atoms. • All atoms of a given element are identical in size, mass and propertiesAtoms of each element are different. • Atoms cannot be subdivided, created or destroyed. 4. Compounds consist of atoms of different elements combined together. Compounds have constant composition (fixed ratio of atoms). 5 Chemical reactions involve the rearrangement of those atoms.
Through observation and experimentation we have found that some are true, others are not! • All matter is made of tiny particles called atoms. • All atoms of a given element are identical in size, mass and properties • Atoms of each element are different. • Atoms cannot be subdivided, created of destroyed. 5. Compounds consist of atoms of different elements combined together. Compounds have constant composition (fixed ratio of atoms). 6. Chemical reactions involve the rearrangement of those atoms.
Dead Dude #3J.J Thomson- 1850 A ball of positive mass containing a number of electrons that are embedded. Getting the idea that there are protons and electrons (nucleus).
Shortcomings Doesn’t explain the existence of electrons outside the nucleus or their importance in bonding. No neutrons- can’t explain radioactivity or the existence of isotopes.
What did experiments with the cathode ray tubes teach us? http://www.youtube.com/watch?v=O9Goyscbazk&safety_mode=true&persist_safety_mode=1&safe=active
Late 1800’s Discovery of and experiments using the cathode ray tube led to our understanding of the electron.
Millikan Oil Drop Experiment Millikan Oil Drop Experiment We learned what the actual charge of an electron is– pretty cool!
Henri Becquerel- 1897 Researched newly discovered X-rays (Phosphorescence). Accidently discovered that uranium emits radiation that could be measured using photographic plates. Discovered Radioactivity- electrically charged particles.
The Dr’s Curie- 1898 Discovered new elements- Polonium and Radium. Very unstable elements that give off energy. This led to an under- standing of Alpha, Beta and Gamma particles.
Dead Dude #4 • Rutherford Model- 1905 • Mass of the atom is concentrated in the center of a positively charged region called the nucleus. • The Planetary Model
Gold Foil Experiment- Draw this and write about the experiment.
Ask Ben… Gold Foil Experiment
Shortcomings Doesn’t place the electrons. Doesn’t include neutrons.
Warm Up- Leave enough space to finish the atomic theory ppt (2 more slides) The actual mass of a proton is 1.673 X 10-27 kg. a. What is the mass of 6300 protons? b. Convert your answer to decigrams. c. Convert your answer to megagrams.
Bohr Model-1920 Believed that electrons traveled in precise orbits around the nucleus of an atom
Schrodinger Quantum Mechanical Model. Describes mathematically the wave properties of electrons and other very small particles The nucleus is at the center of the atom and the electrons are in the electron cloud.
Build an Atom Activity… Get a computer… type in Build an atom phet Write everything in bold print Answer every question… You have about 35 minutes to get this done!
Draw the Bohr Model for the following atoms…. Na N Cl The octet rule says that atoms will be more stable when they have a full outer shell… usually 8 valence electrons.
Ions Ions are atoms that gain or lose electrons to obtain a full outer shell (a complete octet). Cations- lose electrons Anions - gain electrons
Ions • The number of protons does not change in an ion • The number of neutrons does not change in an ion. • So, both the atomic number and the atomic mass remain the same.
How do I calculate the average atomic mass of an element? Look at just about any element on the periodic table. Do you notice that most of the atomic masses listed are not whole numbers.
Hmmmmm…….. Can we have a part of a proton or neutron? I don’t think so!
What we are looking at is the average atomic mass of the isotopes.Some Kr atoms are 83amuothers are 84amu
So… how do they get that number? The calculation: 1. Write the percent abundance (given) 2. Change to relative abundance 3. Multiply relative abundance by mass 4. Add’em up! Easy as pie!
