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Energy, Atoms and Molecules The capacity to do work or produce heat Measured in calories or Joules Law of Conservation of Energy: E is neither created nor destroyed Temperature is a way to measure heat energy. Energy Celsius vs Kelvins Anything with mass and volume Physical changes = crushing, tearing, state changes Chemical Changes = alter the chemical identity of the substance Matter Matter is neither created nor destroyed Law of Conservation of Matter A substance that cannot be separated into simpler substances by chemical change. Elements are composed of atoms. Elements Making the Periodic Table of Elements via Stellar Evolution Helium Fusion in Stars Creating Carbon and Beyond Up to Iron The Relative Abundances of the elements reflect these fusion reactions. Elements divisible by 4 are the most abundant. Where did elements come from? Learn the first 54 element symbols ! Hydrogen (#1) = H Helium = He Lithium = Li Beryllium = Be To (#54) Xenon = Xe What Symbols? Nemonics and tools: Au, give me your gold! Cu in the copper mine! Did you hear about the date between oxygen and potassium? (it was OK)! Did you hear about the date between oxygen and magnesium? (it was OMG)! Two or more atoms bonded together. Compounds Heterogeneous- visibly different parts of a mixture Homogeneous- looks the same throughout Mixtures Atoms are unbelievably tiny. How tiny? Incredibly smaller than plant and animal cells. Billions of atoms make up the writing tip of your pen or pencil. Atomic Size Atom Characteristics All matter is made of atoms. Space (without any particles) has no atoms. Atoms are made of smaller particles protons + neutrons ( ) and electrons (-) Protons, neutrons, and electrons, of course, are made of even smaller particles… Protons, electrons and neutrons are made of even smaller particles including, Quarks, bosons, fermions, mesons, etc. Particle physics studies these entities (you don’t need to know these in Chem 1 &2). Sub-subatomic particles Positvely charged Equals the atomic number of an atom. Always stays the same for an element. Located in the nucleus of the atom. Protons Neutral charge Number of neutrons = Atomic mass minus the atomic number. Different isotopes have different numbers of neutrons. Always reside in the nucleus. (a neutron walked into a bar) Neutrons Negative electrical charge Electrons equal protons in atoms. Missing electrons make positive ions. Extra electrons make negative ions. Located in shells outside nucleus. Electrons Hot or Not? The End of Part 1 Definitely HOT! ISOTOPES Many elements have different types of atoms, each with different numbers of neutrons. Each type is called an isotope. Hydrogen has 3 isotopes: H-1, H-2 and H-3. Isotopes with higher numbers of neutrons than normal tend to be radioactive. For example, H-3 or tritium isotopes tend to spontaneously give off electrons called beta particles. This is called radioactive decay. How do they do this? Isotopes Radioactivity Most elements have isotopes that give off neutrons or protons or electrons spontaneously into space at high speeds. Alpha Particle = 2 protons and 2 neutrons Beta Particle = electron Gamma Ray = electromagnetic wave. All three types of radiation are ionizing (dislodge electrons and cause chemical reactions to happen) Radiation Types Penetrating Power paper stops alpha aluminum foil stops beta thick lead or concrete stops gamma Natural Radioactive Decay http://www.visionlearning.com/library/mo dule_viewer.php?mid=59 http://www.furryelephant.com/player.php ?subject=physics&jumpTo=re/2Ms4 Nuclear Chemistry Review Links The average atomic mass (protons and neutrons) is the weighted average of the different isotopes. weighted mass = % abundance X mass Finding Average Atomic Mass % abundance X mass = weighted mass Cl-35 75.53 x 34.97 = 26.41 Cl-37 24.47 x 36.97 = 9.04 Average atomic mass = 35.45 Ions Sodium has 11 protons and 11 electrons. When it loses an electron, it becomes a cation with a +1 charge, Na+1 Chlorine has 17 protons and 17 electrons. When it steals sodium’s electron, it will have 18 electrons, and becomes an anion with a –1 charge. Cl-1 +cations and - anions Ion Examples Positive and negative ions are attracted to each other and form ionic bods to make a compound. Na+1 Sodium Cl-1 and chlorine bond to each other to become a formula unit of sodium chloride. Hot or Not? Atoms and Compounds: Definitely HOT! The End