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Elements, Atoms, and Ions

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  • 1. Elements, Atoms, and Ions
  • 2. Elements The most abundant elements are: C, H, O, N (P, S) Trace elements necessary for human function in small amounts include: Cu, I, F
  • 3. Elements & their names/symbols Element names reflect either their properties, the city of their discovery, or are given in honor of a scientist (not necessarily the discoverer of the element) Symbols always start with a capital letter. If it has more than one letter, all other letters are in lower case The first letter of the element symbol is the first letter of the element name. However it may either be based on its English or Latin origins (ex: Sodium is Na for natrium.
  • 4. Atoms & Compounds Dalton’s Atomic  Elements are pure Theory is a substances compilation of the  Mixtures of pure observations of substances are called scientists about atoms compounds in the 1800s.  Proportions in Those observations compounds are fixed include: (the law of constant composition)
  • 5. Dalton’s Atomic Theory Elements are made of tiny indivisible particles called atoms All atoms of a given element are identical Atoms of an element are different from the atoms of a different element Atoms of one element can combine in fixed ratios with atoms from another element to form compounds Atoms are neither created nor destroyed in chemical reactions, but are simply recombined
  • 6. John Dalton Published a periodic table of elements based on atomic weights in 1803 He was interested in predicting the behaviors of substances based on their properties as organized in his table His accomplishments include discoveries in chemistry, meteorology, & medicine (color blindness)
  • 7. John Dalton’s Atomic Theory http://www.youtube.com/watch?v=HFF- 2wyyTKc
  • 8. Compounds Chemical formulas represent the types and numbers of atoms in a compound. Numbers are written as subscripts to the right of each element symbol, representing the number of atoms of that element in the compound NO2
  • 9. Atomic Structure Atoms consist of three particles: protons, neutrons, and electrons Protons and neutrons make up the center known as the nucleus. Protons have a positive charge while neutrons are electrically neutral Electrons circle around the nucleus in energy levels (aka shells) and have a negative charge
  • 10. Evolution of the Atomic Model The Greeks named the atom after the word ‘atomos’ meaning indivisible
  • 11. Evolution of the Atomic ModelThomson’s plum pudding model based on the cathode ray tube experiments in the late 1800s (1897) showed that there were negatively charged particles in the atom
  • 12. Cathode Ray Experiment http://www.youtube.com/watch?v=JwdGF ZA3WOs http://www.youtube.com/watch?v=RW_zf KOU9uM
  • 13. Evolution of the Atomic Model Rutherford and the Plum pudding vs. gold foil experiment Rutherford’s model (1911) showed that those negatively charged particles were located outside a dense positively charged center he termed the nucleus
  • 14. Gold Foil Experiment http://www.youtube.com/watch?v=5pZj0u _XMbc http://www.youtube.com/watch?v=bSEO OMs5VNU
  • 15. Evolution of the Atomic Model Bohr’s model (1913) aka the Rutherford- Bohr model gave more details as to the location of electrons around the nucleus Work based on line emission spectra It showed the electrons in circular paths around the nucleus called orbits
  • 16. Evolution of the Atomic ModelModern theory of atomic structure Broglie and Shrodinger (1924, 1926) showed the electrons show some wave like behavior and we can predict their location around the nucleus in terms of probabilities.
  • 17. Modern Atomic Theory From this stemmed the idea of electrons arranged in orbitals at varying distances from the nucleus
  • 18. Isotopes Two atoms of the same element with same number of protons and electrons but differing numbers of neutrons (differing mass numbers) Because the name of an element is determined by the number of protons (atomic number)
  • 19. Mass & Atomic NumbersMass number (# of p + n) –Atomic number (# of p)# of neutrons in the atom
  • 20. The Periodic Table Periods are the horizontal rows Groups (families) are the vertical columns
  • 21. Metals, Nonmetals, & MetalloidsMetals: Non Metals: Shiny  Are none of these Solid (except Hg) things Good conductors of heat Metalloids: Good conductors of  aka semiconductors electricity  Have some metallic Malleable properties to some Ductile degree in some situations
  • 22. Major groups of the P.T. Main element groups (tall columns) Alkali metals (AM) +1 Alkaline earth metals (AEM) +2 Halogens (halo=salt) -1 Noble gases (inert) no ions formed Transition metals ion formation varies Lanthanide/actinide series (radioactive)
  • 23. Main Element Groups All other main element groups go by the name of the first element in the group (ex: Boron family)
  • 24. Periodic Table History Mendeleev is credited with putting together the first periodic table in the 1860s Mendeleev’s table was organized using atomic weights of elements It was an important breakthrough because he was able to predict the properties of elements not yet discovered at the time
  • 25. Periodic Table History Mendeleev’s table revealed patterns in valence electron #s and properties of elements within the same group (family) http://www.youtube.c om/watch?v=inwaqkj a6TE
  • 26. Periodic Table History Henry Moseley in 1914 was able to use modern technology to determine that the atomic number was a better way of organizing the periodic table first created by Mendeleev. Organizing it this way increased the progressive and predictive capabilities of the table Our modern day periodic table is organized by atomic number
  • 27. Diatomics Some elements exist in pairs of atoms called diatomic molecules They include (and you need to memorize) the following: H2 N2 O2 F2 Cl2 Br2 I2
  • 28. Atoms vs. Ions Atoms are neutral overall but can lose/gain electrons to form ions (atoms with a charge) You can predict ion formation by using the periodic table Elements in the left hand columns lose electrons to form positive ions (cations) Elements in the right hand columns gain electrons to form negative ions (anions)
  • 29. Ionic Compounds Are formed when negatively and positively charged ions are attracted to each other in order to regain a neutral charge overall. The ions bond in numbers that will allow for a net charge of zero (neutral) or they won’t bond at all For example: F- and H+ form the ionic compound HF Ca+2 and Br- form the compound CaBr2

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