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CEM 141 exam 3 Questions & 100% Verified Correct Answers with complete solutions (Latest update
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CEM 141 exam 3 Questions & 100% Verified Correct Answers with complete solutions (Latest update
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CEM 141 exam 31) count valence electrons (total)
2) write the skeleton structure
3) use 2 electrons for each bond
4) starting with the outside atoms, make sure each atom (except H or B) has 8 valence
electrons by adding lone pairs
5) if there are not enough electrons, form multiple bonds - ANS-Draw Lewis structures when
given the molecular formula of hydrocarbons (including multiple bonds), and compounds
containing C, H, N, O, F, Cl, Br, I ,P, and S.
be able to predict polarity based on knowing how to measure electronegativity on the periodic
table and be able to draw shapes of bonds based on VSEPR - ANS-Predict the polarity of
bonds using atom electronegativity. Predict the polarity of molecules using bond polarity and
molecular shape.
because for metals it is easier for them to lose an electron and nonmetals it is easier for them to
gain an electron because it is closer for them to get to a full valence shell - ANS-Explain why
metals tend to form positive ions and nonmetals tend to form negative ions. Predict the charge
on common single atom ions.
discrete atoms: lower melting/boiling points, are not diatomic
small molecules: lower melting/boiling points, diatomic, lower because are only held together by
LDFs, which are substantially weaker than continuous extended networks
continuous extended networks: higher melting/boiling points, higher because covalent bonds
have to be broken in order to turn solids to liquids, liquids to gas - ANS-Predict, draw models
(pictures), and explain why relative melting points and boiling points for substances that exist as
molecules (like H2) differ from those that exist as continuous extended networks (like diamond
or metals).
hydrogen bonds: occur between hydrogen and oxygen, fluorine, or nitrogen
dipole dipole: polar interactions!!
LDFs: in all reactions except ions - ANS-Use molecular structure and the polarity of a molecule
to predict the type(s) of IMFs (LDFs, dipole-dipole interactions, and hydrogen bonding
interactions) present in molecules.
Ionic compounds contain one nonmetal and one metal. They generally have high boiling points
because lots of energy is required to break the ion-ion interactions. - ANS-Describe the
structure of ionic compounds. Use the structure to explain the properties of ionic compounds
(ex: melting point, boiling point, hardness, and ability to conduct electricity). Predict and/or rank
relative melting and boiling points of given compounds.
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