CHEM 111- Test #4

Which statement best describes the energy change when a chemical bond is formed? a)the system becomes more stable and energy is released b) energy is required to form a bond and energy is stored within c) no overall energy change d) depending on the bond energy can be released or absorbed

a)The system becomes more stable and energy is released

What is resonance stabilization?

A molecule or ion with resonance structures is more stable. *resonance creates stability*.

What is molecular orbital theory?

Describes an orbital that surrounds a entire molecule where any electron can be found. Explains resonance. molecular orbitals rather than atomic orbitals

What is an isomer?

Compound with same atoms, but arranged differently. Different atoms are attache to each other

Determine the shape and polarity of: NO2 +

Linear; dipoles cancel so non-polar

What's the hybridization for octahedral electron geometry?

d2sp3 (orbitals 6d2sp3)

What's the hybridization for trigonal bipyramidal electron geometry?

dsp3 (orbitals 5dsp3)

Draw the Lewis structure and determine the shape and electron geometry for: H2O

e geo: tetrahedral shape: bent

Draw the Lewis structure and determine the shape and electron geometry for: NH3

e geo: tetrahedral shape: trigonal pyramidal

Draw the Lewis structure and determine the shape and electron geometry for: SOCl2

e geo: tetrahedral shape: trigonal pyramidal

What's a sigma bond?

end's of the orbitals overlap; single bonds, 1st bond in a single or triple bond

Determine the shape and polarity of: HBr

linear; polar Br is more electronegative so that side of the molecule is more negative

What's the VSPER geometry around IF5?

octahedral

Is SF4 polar or non-polar?

polar because not all evenly spaced out

What is an equivalent resonance structure?

same molecule and the same type of bonds. also the same number of each type of bond.

What is an in-equivalent resonance structure?

same molecule, but different types if bonds and changes in formal charges

What's a pi bond?

side-on overlap; 2nd bond in a double bond or 2nd & 3rd bond in a triple bond

What is the hybridization for CH2O and how many pi and sigma bonds are there?

sigma: 3 pi: 1 since CH2O is trigonal planar the hybridization is sp2

What's the hybridization for linear (180) electron geometry?

sp (orbitals 1sp and 2 p)

What's the hybridization for trigonal planar (120) electron geometry?

sp2 (orbitals 3sp2 and 1 p)

What's the hybridization for tetrahedral (109.5) electron geometry?

sp3 (orbitals 4 sp3)

Draw the Lewis structure and determine the shape and electron geometry for: CH4

tetrahedral for both

Determine the shape and polarity of: NH4 +

tetrahedral; non-polar dipoles cancel out

Determine the shape and polarity of: CH3F

tetrahedral; polar

Determine the shape and polarity of: CH2O

trigonal planar; polar