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2012-10-31 16:53:05
vet tech chemistry compounds bonds set

vet tech chemistry compounds and bonds set
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  1. Anion
    • a negatively charged ion, such as Cl-
    • gained 1 or more electrons
  2. Cation
    • a positively charged ion, such as Na+
    • lost 1 or more electrons
    • all are from metals including H+ and NH4+
  3. Covalent compound
    • a combination of atoms in which noble gas arrangements are attained by sharing electrons
    • shared valence electrons
    • 2 non-metals:
    • writing electron dots:
    • - exist list - total # valence electrons from all atoms in the compound, plus/minus charge
    • - wish list - total # electrons that all atoms in compound would like to have (nearest noble gas)
    • - wish list - exist list = # of bonding electrons
    • naming:
    • - end in -ide
    • - use Greek prefixes to show how many of each atom needed. Mono- may be left off 1st atom.
  4. Dipole
    the separation of positive and negative charges in a polar bond indicated by an arrow that is drawn from the more positive atom to the more
  5. negative atom
    • covalent molecules where one end of it is + and the other end of the molecule is - because:
    • - there is at least one polar covalent bond in the molecule
    • - the molecule is asymmetrical or uneven in its shape
  6. Dipole-dipole attraction
    attractive forces between oppositely charged ends of polar molecules
  7. Dispersion forces
    • weak dipole bonding that results from momentary polarization of non-polar molecules
    • aka London forces, Van De Walls forces
    • weak forces from temporary dipoles between non-dipoles (happens occassionally when an electron orbits one bonded atom more than the other bonded one)
  8. Double bond
    a sharing of 2 pairs of electrons by 2 atoms
  9. Electronegativity
    the relative ability of a element to attract electrons in a bond
  10. Electronegativity difference rule
    • <0.4 => non-polar covalent bond
    • 0.4 - 1.8 => polar covalent bond
    • > 1.8 => ionic bond
  11. Formula
    the group of symbols and subscripts that represents the atoms of ions in a compound
  12. Hydrogen bond
    the attraction between a partially positive H atom and a strongly electronegative atom of F, O or N.
  13. Intermolecular forces (attractive forces in compounds)
    • in order of decreasing strength:
    • - hydrogen bonding
    • - dipole-dipole attraction (for polar molecules)
    • - dispersion forces
  14. Ion
    • an atom or group of atoms hanving an electrical charge because of a loss or gain of electrons
    • charged atom or group of atoms because of a loss or gain of electrons
  15. Ionic bond
    • a simple attraction between 2 opposite charged ions after their atoms have transferred or exchanged electrons
    • metal with non-metal
  16. Ionic charge
    the difference between the number of protons (positive) and the number of electrons (negative) written in the upper right corner of the symbol for
  17. the element or polyatomic ion
  18. Ionic compound
    • a compund of positive and negative ions held together by ionic bonds
    • writing binary ionic compounds:
    • - the + metal ion is always placed 1st, the non-metal - ion is placed last; the compund ends in -ide
    • compounds whose metals have variable charges:
    • - roman numeral after metal indicates charge (+) of metal.
  19. Molecule
    the smallest unit of 2 or more atoms held together by covalent bonds
  20. Non-polar covalent bond
    a covalent bond in which the electrons are shared equally between the atoms
  21. Non-polar molecule
    a molecule that has only non-polar bonds or in which the bond dipoles cancel
  22. Octet
    a set of 8 valence electrons
  23. Octet rule
    • elements in Groups 1A-7A (1, 2, 13-17) react with other elements by forming ionic or covalent bonds to produce a noble gas arrangement
    • usually 8 electrons in the outer shell
    • atoms react such that they gain, lose or share electrons so as to have a total of 8 electrons in their valence (noble gas configuration)
  24. Polar covalent bond
    a covalent bond in which the electrons are shared unequally between atoms
  25. Polar molecule
    a molecule containing bond dipoles that do not cancel
  26. Polarity
    a measure of the unequal sharing of electrons indicated by the difference in electronegativity
  27. Polyatomic ion
    • a group of covalently bonded non-metal atoms that has an overall electrical charge
    • ions composed of many (> 2) atoms, but act as a single ion with a single overall charge
    • many are oxyanions
    • many end in -ate or -ite; exceptions - Hydroxide OH-, cyanide CN-, ammonium NH4+ (cation)
    • Naming:
    • - metal placed 1st
    • - polyatomic ion is placed last and is recognized as such, eg parenthesize if > 1 ion (needs subscript)
    • hint - if ther are 3 types of atoms in the molecultes, then 90% of the time there is a polyatomic ion
  28. Triple bond
    a sharing of 3 pairs of electrons by 2 atoms
  29. Valence-shell electron-pair repulsion (VESPR) theory
    a theory that predicts the shape of a molecule by placing the electron pairs on a central atom as far apart as possible to minimize the mutual repulsion of the electrons