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Chemical Spill in High School Lab

Chemical Spill in High School Lab January 26, 2006 - Five people needed hospital treatment after a chemical spill inside Middle Township High School in Cape May County.

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Chemical Spill in High School Lab

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  1. Chemical Spill in High School Lab • January 26, 2006 - Five people needed hospital treatment after a chemical spill inside Middle Township High School in Cape May County. • Police say it happened around 4 Thursday afternoon after school had been dismissed. Officials say some students in a lab classroom dropped a gallon of acetic acid. Hazardous materials crews were called in to clean it up. • Five people were overcome by the fumes. They were treated and released from area hospitals. School will be open as usual Friday.

  2. Bonding and Geometry

  3. Dmitri Mendeleev • In 1869, came up with the idea to arrange the known elements in a table. • Arranged them in order of increasing atomic mass. • He left blanks where he knew as yet undiscovered elements should go.

  4. Henry Moseley • In 1913, arranged the elements in order of increasing atomic number • In 1869, Mendeleev did not know about protons yet. • When arranged this way, there are patterns in their physical and chemical properties (The Periodic Law)

  5. Periodic Properties • Density • Atomic radius (size) • Electronegativity—ability of an atom to attract electrons in a bond • Ions and charges within a group • Ionization energy—energy required to remove an electron from an atom

  6. Valence Electrons • Valence e- --e- that exists at the highest energy level of that element’s atoms • Outermost electrons • Only electrons involved in bonding • Group # = no. of valence e-

  7. Lewis Dot Diagrams • Shows the element symbol with valence electrons as dots.

  8. Octet rule • An atom can achieve a full valence (octet) by becoming an ion, but also by bonding with another atom. Bonding allows the two or more atoms to exchange or share atoms. • Metals will lose electrons & form cations to gain an octet. • Nonmetals will gain or share electrons to gain an octet.

  9. Bonding • There are two types of bonding: • IonicCovalent(molecular) • Metal to nonmetal Nonmetal to nonmetal • Called a salt Called a molecule • Electrons are handed over Electrons are shared • Opposite charges hold Can be single or them together multiple bond

  10. Bonding in Metal Atoms

  11. Bonding • The difference in electronegativities of the two atoms in the bond will determine what kind of bond it is: • Ionic (>2.0) electrons handed over • Polar covalent (0.4 – 2.0) unequal sharing of electrons • Nonpolar covalent (<0.4) virtually equal sharing

  12. Octet Rule & Bonding • Lewis Structures of molecules are diagrams that depict the electron arrangement in a molecule • For instance: Chlorine (Cl2)

  13. Lewis Structures • Count the # of valence electrons each atom in the molecule has. • Total them. • Distribute that many valence electrons among the molecule so that every atom has a full valence (8). • Note: hydrogen only needs two. • Multiple bonds may be necessary.

  14. Ionic vs Covalent Properties • IonicCovalent(molecular) • Solids @ room temp. Could be any phase • Very high melting pt. Low melting pt. • Conduct elec. in H2O Do not conduct • Form brittle crystals Form countless types of compounds

  15. Geometry • VSEPR Theory—repulsion between electron pairs in a molecule cause them to shift so that they will be as far away from each other as possible. • This repulsion causes molecules to have the shapes (geometry) that they have.

  16. Geometry • Linear—two or more atoms in a straight line

  17. Bent—bond angle is 104.5° • Trigonal—atoms form a triangle in a single plane

  18. Pyramidal-central atom surrounded by three atoms and an electron pair • Tetrahedral-central atom surrounded by four atoms

  19. Polarity (Bonds) • A molecule can have a nonpolar covalent bond. • A molecule can have a polar covalent bond. • This occurs when a highly electronegative atom (O, F, Cl or N) is bonded to a less electronegative atom. • In a polar bond, there is an uneven distribution of charge.

  20. Polarity (Molecules) • A molecule can also be polar or nonpolar. • Polarity of a molecule occurs when there is an uneven distribution of charge throughout the entire molecule. This is called a dipole. • This can occur due to two factors: the bonds in the molecule, and the shape (geometry) of the molecule.

  21. Polarity (Molecules) • H2O • C2H6 • CH4 • CH3F • CO2 • A polar molecule will have drastically different properties than a nonpolar molecule.

  22. Polarity • Generally speaking: • If it’s bent, it’s polar. • If it’s pyramidal, it’s polar. • If it’s linear w/2 identical atoms, it’s nonpolar. • If it’s linear w/O,N,F,CL and a diff’t atom, it’s polar. • If it’s a tetrahedral w/4 identical atoms, it’s nonpolar. • If it’s a tetrahedral w/3 identical atoms and one atom of O,N,F or Cl, it’s polar.

  23. Erwin Schrödinger’s Model1926 • Mathematical equations describe the motion of electrons.

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