Exam 1 Review [Version 2]- Spring 2006 - Sparks

Exam 1 Review [Version 2]- Spring 2006 - Sparks - a The...

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1. Differences between: ionic forces, dipole forces, dispersion forces, and covalent bonds. a. dispersion forces are only important in molecules that are not polar. You can tell if a molecule is polar by looking at its molecular geometry and then assessing: Is the molecule symetrical? (both shape, and atoms in the molecule). If so, then it should not be polar. You should also check if there is a difference in electronegativity between atoms that are making up the molecule. If the molecule is not symetrical, and there is a difference in electronegativity between atoms in the molecule, then the molecule is polar. Polar molecules are subject to dipole-dipole intermolecular forces. As for covalent bonds, they fall into the category of intramolecular forces. If you need more help understanding, feel free to come by office hours on Wednesday. 2. Atomic #
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Unformatted text preview: a. The atomic number is always equal to the number of protons in an atom. In a neutral atom, there are equal numbers of protons and electrons, so the atomic number is also equal to the number of electrons. In an ion, the atom has gained or lost some electrons, so the atomic number is no longer equal to the number of electrons. Let's look at a couple of examples: S^(2-) (sulfur with a negative 2 charge): In a neutral atom there would 16 protons, 16 electrons, and no net charge. Since there is a net charge of -2, we know there are two extra electrons. There are ALWAYS 16 protons in S, so there must now be 18 electrons. Na+: In a neutral atom there would 11 protons, 11 electrons, and no net charge. Since there is a net charge of +1, we know there is one more proton than electron. There are ALWAYS 11 protons in Na, so there must now be 10 electrons....
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