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Accurate definitions

  1. Dec 17, 2008 #1
    I've been learning chemistry for a good while and now I'm doing it in college and what I've noticed is I don't do well in tests because I have trouble explaining what I know. Even though I understand the concept my answers aren't always adequate and I lose marks. Can anyone recommend a site that gives the most accurate and concise definitions of chemistry terms? I'm not gonna memorize definitions but I'd like to see how these things are defined by the pros.

    I already know most of whats gonna be on the test. For example one of them will be "Explain what a covalent bond is". I know well what a covalent bond is but heres how I'd answer it. "A covalent bond is a chemical bond in which two atoms with small differences in electronegativity share their valence electrons so that each atom has 8 electrons in their outer shells."

    Is that a reasonable answer? The problem I find is that the teacher might assume I have a lack of understanding because I don't mention everything for example I left out "the reason each atom ends up with 8 electrons is because their combined valence electrons amount to 8 so technically they have complete octets". I write slowly so I can't give big 5 line answers for every question.

    Another problem is my terminology. The teacher never thought the class the word "valence electrons" he just refers to them as "electrons in the outer energy level of the atom" and he never says octet so he might take marks off me for not explaining it his way.

    Any suggestions on how I should deal with this test? The teacher doesn't give out notes so I cant memorize his definitions. I don't like memorizing definitions though I learn the concepts and then define as best I can. Its more of an English test than a chemistry test in my case cuz the hard parts properly explaining what I know.
     
  2. jcsd
  3. Dec 29, 2008 #2
    To begin with, a covalent bond does not require that each atom forms an octet; it just brings the two atoms to a higher stability through the sharing of an electron. Also, small is a relativistic term, which does not make good scientific definitions. You might want to put down exact numbers, if you wish to characterize how electronegativity differences play a role the polarity of the molecule; however, I highly doubt that the teacher was looking for this explanation and wanted a much more elementary definition. A definition for covalent bond that I would use in your circumstances would be "a bond between two atoms in which an electron is shared to achieve a more stable situation for the two atoms through the creation of a molecule." An example of why you cannot simply define a covalent bond as an octect forming situation is that of boron compounds and the various spd hybridized compounds, in case you are confused as to why it does not necessarily form an octet. Also, more than one covalent bond is able to be formed on a single substituent atom of a molecule.

    With that said, science does require proper mastery of English and mastery of a precise theoretical standpoint of how you are able to describe things. The definition you gave, and I'm very sorry to possibly offend you, is wrong. I too was like you when I first took a real science class and did not use precise wording for concepts, but once you learn some more, you will realize precision equates mastery.

    Overall, you were wrong, and your teacher is right. Spend more time on reading the textbook and thinking about why each word is there in a definition.

    Good luck.
     
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