Chapter 7 Test Flashcards
sigma bonds form when atomic orbitals overlap _______
end to end on the bond axis
what is needed to form a covalent bond avcording to the valence bond theory?
unpaired electrons with opposite spins
pi bonds form when the atomic orbitals overlap _________
side to side parallel to the bond axis
____ bonds are weaker than _____ bonds but always form in conjunction with a _____ bond, so the two bonds acting together are stronger than either by itself
pi, sigma, sigma
according to the molecular orbital theory, bonding orbitals are higher in energy than the atomic orbitals from which they form. True or False
false
which of these molecules does not contain polar bonds
CH4
what shape does water molecule form
bent
what is the molecular shape eof CCl4
tetrahedral
the entire molecule of CCl4 is _____
non polar
draw the lewis structure for BeH2
H—Be–H
Why is a sigma bond stronger than a pi bond?
because the region of highest electron probability lies on the bond axis
How do single and double bonds behave in a molecule that exhibits resonance?
they all experience resonance
How does boron’s position in the periodic table hint that it is stable when bonded to only three atoms?
only 3 valence electrons; not a metal so it is most likely to give up the 3 to form ionic compound
What two characteristics of liquid oxygen contradict pre- dictions from the valence bond theory but are explained by the molecular orbital theory?
pale blue in color, and demonstrated magnetic attractions (attracted to magnetic field)
Discuss the difference between the tetrahedral, pyramidal, and trigonal planar molecular geometries.
tetrahedral- involves 5 atoms, one in the central and one atom at each verices
pyramidal- involves 4 atoms, 3 outer atoms
trigonal planar- involves 4 atoms, central atoms bonded to 3 outer atoms
Explain how a tetrahedral molecule could have a dipole moment.
molecule is asymmetrical
All sublevels hold the same total number of electrons.
true or false
false
A triple bond consists of a single sigma bond and two pi bonds. (An example of a molecule with a triple bond is atmospheric diatomic nitrogen.)
True or false
true
The atmospheric pollutant sulfur dioxide (SO2), a molecule exhibiting resonance, has single and double bonds that switch back and forth so rapidly that chemists cannot detect their state.
True or false
false
_____ region connects 2 nuclei where high electron density forms
bond axis region
the location of ____ bonds maximize effectiveness of _____ attraction
sigma, electrostatic
why are pi bonds weaker than sigma bonds?
the electrons are spread out over a greater volume of space around bond axis
what forms the strongest bond between atoms?
triple
what are the 3 exceptions to the octet rule and an example of each
- molecules with an odd number of valence electrons to share has 1 pair short an electron (nitrogen dioxide NO2)
- molecules with fewer than 4 pairs of shared electrons (boron)
- molecules that have more than 8 valence electrons are shared with central atom (sulfur hexafluoride SF6)
