Chapter 7 Test Flashcards

0
Q

sigma bonds form when atomic orbitals overlap _______

A

end to end on the bond axis

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1
Q

what is needed to form a covalent bond avcording to the valence bond theory?

A

unpaired electrons with opposite spins

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2
Q

pi bonds form when the atomic orbitals overlap _________

A

side to side parallel to the bond axis

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3
Q

____ 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

A

pi, sigma, sigma

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4
Q

according to the molecular orbital theory, bonding orbitals are higher in energy than the atomic orbitals from which they form. True or False

A

false

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5
Q

which of these molecules does not contain polar bonds

A

CH4

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6
Q

what shape does water molecule form

A

bent

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7
Q

what is the molecular shape eof CCl4

A

tetrahedral

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8
Q

the entire molecule of CCl4 is _____

A

non polar

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9
Q

draw the lewis structure for BeH2

A

H—Be–H

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10
Q

Why is a sigma bond stronger than a pi bond?

A

because the region of highest electron probability lies on the bond axis

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11
Q

How do single and double bonds behave in a molecule that exhibits resonance?

A

they all experience resonance

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12
Q

How does boron’s position in the periodic table hint that it is stable when bonded to only three atoms?

A

only 3 valence electrons; not a metal so it is most likely to give up the 3 to form ionic compound

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13
Q

What two characteristics of liquid oxygen contradict pre- dictions from the valence bond theory but are explained by the molecular orbital theory?

A

pale blue in color, and demonstrated magnetic attractions (attracted to magnetic field)

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14
Q

Discuss the difference between the tetrahedral, pyramidal, and trigonal planar molecular geometries.

A

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

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15
Q

Explain how a tetrahedral molecule could have a dipole moment.

A

molecule is asymmetrical

16
Q

All sublevels hold the same total number of electrons.
true or false

A

false

17
Q

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

A

true

18
Q

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

A

false

19
Q

_____ region connects 2 nuclei where high electron density forms

A

bond axis region

20
Q

the location of ____ bonds maximize effectiveness of _____ attraction

A

sigma, electrostatic

21
Q

why are pi bonds weaker than sigma bonds?

A

the electrons are spread out over a greater volume of space around bond axis

22
Q

what forms the strongest bond between atoms?

A

triple

23
Q

what are the 3 exceptions to the octet rule and an example of each

A
  1. molecules with an odd number of valence electrons to share has 1 pair short an electron (nitrogen dioxide NO2)
  2. molecules with fewer than 4 pairs of shared electrons (boron)
  3. molecules that have more than 8 valence electrons are shared with central atom (sulfur hexafluoride SF6)
24
Q

what are the results of bonding orbitals?

A
  1. electrons stabilize.
  2. they are lower in energy
  3. (results in) energy stored in bonds
25
Q

what is the VSEPR theory

A

valence shell electron pair repulsion

VSPER focuses on the location of highest electron density surrounding the central atom in a molecule

26
Q

ClO2- is whAt shape?

A

Bent

27
Q

NI3 is what shape

A

Trigonal planar

28
Q

Br2CO is what shape?

A

Pyramidal