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Ch 18– Properties of Matter

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  1. 18.1 – Atomic Structure • 3 Subatomic Particles • Each has a charge and mass • Proton: positive charge; found in nucleus • Neutron: neutral (no) charge; found in nucleus • Electron: negative charge; found outside the nucleus in the electron cloud Ch 18– Properties of Matter

  2. Nucleus: made of protonsand neutronsis the central part of the atom; has a positive charge Atoms are neutral; number of protonsequals the number of electrons http://www.lbl.gov/abc/graphics/STRUCTURE.GIF

  3. Atomic Number – start at 1, with the element hydrogen, and go up by one whole number All atoms of the same element will have the same number of protons. Atoms of the same element can have different number of neutrons (isotope) 18.2 -- Comparing Atoms

  4. Atomic number – number of protonsin the nucleus; identifies the atoms, unique for each element Mass number – number of protonsplus the number of neutronsin an atom; helps identify the isotopes Atomic mass (weight)– varies because it is anaverage of all isotopes of an element

  5. Isotope – atoms of the same element but with different number of neutrons Same characteristics – atomic number; number of protons; number of electrons; Same chemical behavior Different characteristics– mass; mass number; number of neutrons; stability Isotopes of Hydrogen: Protium – no neutrons; Deuterium – 1 neutron; Tritium – 2 neutrons http://image.tutorvista.com/content/structurelectronatom/types-of-isotopes-protium-deuterium-tritium.jpeg

  6. Elements are arranged by increasing atomic numbers in a table called the periodic table of elements

  7. This model was proposed by Niels Bohr in 1915; it is not completely correct, but it has many features that are MUST DRAW

  8. EX 1: Atom with 15 proton, 16 neutron, and 18 electron… What is the atom’s net charge? (15+) + (18-) = 3- What is the atomic number of the atom? 15 What is the mass number? 31 This is an atom of what element? phosphorus, P

  9. Why does a nucleus stay together if protonsare repelling each other? • Strong nuclear forces hold protons together when they are close http://www.osha.gov/SLTC/radiationionizing/introtoionizing/slidepresentation/mainpage.html

  10. Energy Levels – 1st level can hold 2 electrons • The remaining levels can hold up to 8 electrons each. • 1st level occupies the lowest energy state • Outermost energy level contain the most energy http://www.physics.uiowa.edu/adventure/fall_2005/oct_15-05/energy_levels.gif

  11. 1808 -- John Dalton published atomic theory which states all matter is composed of tiny particles 18.3 – The Periodic Table of Elements http://www.learner.org/courses/essential/physicalsci/session4/closer3.html

  12. http://www.spbu.ru/files/culture/museums/mendeleev/enmuseum.htmlhttp://www.spbu.ru/files/culture/museums/mendeleev/enmuseum.html • 1871 – Mendeleev organized elements into the periodic table of elements • Similar elements are combined into groups on the periodic table • Valence electronsare located in the outermost region of the electron cloud • Valence electrons are used for classifying which column the element belongs to • Also vary important for bonding purposes

  13. Mendeleev’s Periodic Table – basis for periodic table that we use today http://www.msnucleus.org/membership/html/jh/physical/periodictable/lesson5/periodic5b.html

  14. Today’s Periodic Table

  15. Must Draw