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Chapter 13. The Structure of the Atom. What do you think atoms are and what do they look like?. Opener - Atoms . How did Democritus define atoms?. Atoms are not all the same, they are undying, and always moving
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Chapter 13 The Structure of the Atom
What do you think atoms are and what do they look like? Opener - Atoms
How did Democritus define atoms? • Atoms are not all the same, they are undying, and always moving • All matter is made of indivisible tiny things too small to be seen by the naked eye Democritus – 400 BC
How did Aristotle expand his definition? • Matter is made of atoms and will always exist • He defined the four elements as earth, wind, water and fire Aristotle – 384 BC
What are alchemists? • Scientists who worked on the philosophers stone or the elixir of immortality • Ancient chemistry which led to advances in modern chemistry and the scientific method Alchemists – 500 BC to 1720 AD
How did Lavoisier change the atomic model? • First to name specific elements oxygen and hydrogen • Developed first periodic table with 33 elements Lavoisier - 1777
How did Dalton change it? • Found that elements combine to form compounds • Found that atoms have mass • Started using chemical symbols • Created the billiard ball model Dalton – 1803
How did Thompson change it? • By accident he discovered subatomic particles such as electrons • Developed the plum pudding model Thompson – 1897
How did Rutherford change it? • Discovered that atoms had an atomic nucleus • Found that the nucleus was positive and that electrons were negative • Also that most of an atom is empty space • Gold foil experiment • Developed the planetary model Rutherford – 1898
Particles were shot at a piece of gold foil which hit the nuclei and scattered Rutherford’sGold Foil Experiment
How did Lewis change it? • Made advances in showing how atoms bond together and how they can share electrons Lewis – 1916
How did Bohr change it? • Began the development of the modern model • Electrons are located outside the nucleus in orbitals • Each orbital has a very specific amount of energy Bohr – 1922
What sub-atomic particles are found in a nucleus? • Protons • Charge: +1 • Symbol: p+ • Neutrons • Charge: 0 • Symbol: n0 Nucleus
What are the properties of electrons? • Found orbiting around the outside of the nucleus • Charge: -1 • Symbol: e- Electrons
Person who gives out tickets to traffic court. • Half a dime. • What they do with dead people. • What all that glitters is not. • What you do to cattle that get away. • What a horse has to be if he won’t go for water. • Lone Ranger’s horse. • A really “pressing” thing. • What most lectures are. • Twice a half-nium. • Prisoner who sniffed laughing gas. • Soldier from Troy who only fights after dark. • What a doctor should do for his patients (2 available answers). • Roman streaker who wore shoes with wings. • What I do is none of your _______________! • What the police do to drug houses? • How we refer to the guy who had his stomach removed. • What the Lone Ranger did to his horse Opener - Element Puns
What is an element? • A substance made up of one type of atom • Each atom MUST have the same number of protons, but may have different numbers of electrons (ions) and neutrons (isotopes) The Atom
What is the significance of the atomic number? • Indicates how many protons there are in the element • ONLY way to identify an element Atomic Number
Please find the atomic numbers (number of protons) for: • Hydrogen • Carbon • Silicon • Fluorine • Gold • Potassium • H: 1 • C: 6 • Si: 14 • F: 9 • Au: 79 • K: 19 Atomic Number
How do we figure out the mass of an atom? • Use the atomic mass, which is total mass of all of the sub-atomic pieces • Proton – 1 AMU • Neutron – 1 AMU • Electron – 0 AMU (because its so small) Atomic Mass
How do we figure out how many neutrons are in a nucleus? • Determine the atomic mass • Subtract out the protons (atomic number) • Round DOWN the remaining number (can’t have a part of a neutron) Neutrons
Why don’t we subtract out electrons? • We assume that they have no mass because they are so small Neutrons
Please find the number of neutrons in: • Hydrogen • Carbon • Silicon • Fluorine • Gold • Potassium • H: 0 • C: 6 • Si: 14 • F: 10 • Au: 117 • K: 20 Neutrons
How do we determine the number of electrons in atom? • First determine whether or not the element is neutral or charged (ion) • Neutral – same as the atomic number • Charged – add or subtract the charge to/from the atomic number (Mg2+ or O2-) Electrons
How do I know whether to add or subtract the charge? • Negative charge means you have more electrons ADD • Positive charge means you have less electrons SUBTRACT Remember! Electrons are negative so when you subtract them you are subtracting negatives! Electrons
Where do we place electrons around the nucleus? • Bohr’s orbital model shows us that electrons need to be placed in specific orbitals, shells, or energy levels around the nucleus Electron Placement
How do you place electrons in a Bohr model? • Determine the total number of electrons in the atom or ion • Place the electrons in circular orbitals following the 2-8-8-2 pattern until you have placed all of them Bohr’s Model of an Atom
What is the octet rule? • Atoms “like” to have 8 electrons in the 2nd and 3rd orbitals • 1st orbital is too small to hold 8 electrons • Atoms will react (gain/lose electrons) until they have a FULL outer orbital Bohr’s Model of an Atom
What does carbon’s model look like? • Neutral carbon has 6 electrons • Draw a circular diagram with the following: • 1st orbital – 2 • 2nd orbital – 4 (not full) Bohr’s Model of an Atom
What are valence electrons? • The electrons in the outermost orbital which determine how an element reacts Valence Electrons
Please draw the appropriate Bohr model for: • Li • N • Ne • H • Mg2+ • S2- Bohr’s Model of an Atom
Please draw the appropriate Bohr model for: • Be • Ca • Ar • Na1+ • He0 • H1- • H1+ Opener – Bohr Model Review
How do Lewis dot diagrams simplify Bohr diagrams? • Dot diagrams only show the outer orbital which holds the valence electrons • Ex. Carbon Lewis Dot Diagrams
Please draw the appropriate Lewis dot diagram for: • C • O • F • H • Be2+ • Cl1- Lewis Dot Diagrams