Lewis Dot Structures: Exceptions quiz #1 Flashcards
Lewis Dot Structures: Exceptions quiz #1
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Which compound is an exception to the octet rule? Compounds such as BF3, NO, and SF6 are exceptions to the octet rule because they have atoms with less than or more than eight electrons in their valence shell. Which molecule has only one lone (non-bonding) pair in its Lewis model? Ammonia (NH3) has only one lone pair on the central nitrogen atom in its Lewis structure. How many lone pairs of electrons are on the phosphorus atom in PF3? The phosphorus atom in PF3 has one lone pair of electrons. How many lone pairs of electrons are on the bromine atom in BrF5? The bromine atom in BrF5 has one lone pair of electrons. Which of the following molecules has a Lewis structure that is not consistent with the octet rule? Molecules like BF3, NO, and SF6 have Lewis structures that are not consistent with the octet rule. Which elements should never have expanded octets? Elements in the second period (such as C, N, O, and F) should never have expanded octets. How many lone pairs are on the central atom in BCl3? The central boron atom in BCl3 has zero lone pairs. Which of these compounds could have a Lewis structure with an incomplete octet? Compounds with central atoms from Group 2A or 3A, such as BeCl2 or BF3, can have incomplete octets. Which molecule below would have a Lewis structure that is an exception to the octet rule? NO (nitric oxide) is a molecule with a Lewis structure that is an exception to the octet rule due to its odd number of valence electrons. Which element cannot be the central atom of a Lewis structure? Hydrogen cannot be the central atom of a Lewis structure because it can only form one bond. How many lone pairs are on the central atom in BCl3? The central boron atom in BCl3 has zero lone pairs. How many of the following molecules are hypervalent: PF3? PF3 is not hypervalent; phosphorus in PF3 follows the octet rule. Which structure shown is the correct Lewis structure for XeF4? The correct Lewis structure for XeF4 has xenon as the central atom with four fluorine atoms bonded and two lone pairs on xenon. How many lone pairs are on the central atom of BrF3? The central bromine atom in BrF3 has two lone pairs. Each pictured Lewis structure is invalid. Why might a Lewis structure be invalid? A Lewis structure may be invalid if it violates the octet rule, has incorrect formal charges, or does not account for all valence electrons. What does it mean if there is no valid Lewis structure for a molecule? If there is no valid Lewis structure, it means the molecule cannot be represented without violating basic rules such as the octet rule or correct electron count. Choose the best Lewis structure for SF4. The best Lewis structure for SF4 has sulfur as the central atom with four fluorine atoms bonded and one lone pair on sulfur, resulting in a seesaw molecular geometry. How does adding an atom affect the position of existing atoms or lone pairs in a Lewis structure? Adding an atom can change the arrangement of existing atoms and lone pairs to minimize electron repulsion, often altering the molecular geometry. What is the electron arrangement for a molecule with two single bonds and two lone pairs of electrons on the central atom? A molecule with two single bonds and two lone pairs on the central atom has a bent or angular geometry, like H2O.
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