CHEM 120 unit 3 Exam Questions and Correct
Answers| Latest 2025
2 - ✔✔How many valence electrons does Hydrogen have?
6 - ✔✔How many valence electrons does Boron have?
4 - ✔✔How many valence electrons does Be have?
VESPR theory - ✔✔valence shell electron pair repulsion theory, because electron
pairs repel, molecules adjust their shapes so that valence electrons pairs are as far apart
as possible
central atom - ✔✔What atom can lone pairs only be on?
linear - ✔✔What molecular geometry has two regions?
trigonal planar - ✔✔What molecular geometry has three regions?
tetrahedral - ✔✔What molecular geometry has four regions?
180 - ✔✔bond angle for linear
120 - ✔✔bond angle for trigonal planar
, <120 - ✔✔bond angle for trigonal planar w/ lone pair
109.5 - ✔✔bond angle for tetrahedral
<109.5 - ✔✔bond angle for tetrahedral w/ lone pair
<109.5 - ✔✔bond angle for tetrahedral w/ two lone pairs
Lewis dot structure - ✔✔diagrams that show the bonding between atoms of a
molecule and the lone pairs of electrons that may exist in the molecule
group number - ✔✔What gives the number of valence electrons?
central atom - ✔✔What part of the molecular structure is usually the least
Electronegative?
C, P, N, S - ✔✔What are the most common central atoms?
H, B, Be - ✔✔What three atoms do not have 8 electrons are them in the form of
bonds or lone pairs?
expanded octet - ✔✔- possible for elements in Period 3 or higher due to the
presence of the d orbital
- having more than 8 electrons
incomplete octet - ✔✔central atom is content with less than 8 electrons
Answers| Latest 2025
2 - ✔✔How many valence electrons does Hydrogen have?
6 - ✔✔How many valence electrons does Boron have?
4 - ✔✔How many valence electrons does Be have?
VESPR theory - ✔✔valence shell electron pair repulsion theory, because electron
pairs repel, molecules adjust their shapes so that valence electrons pairs are as far apart
as possible
central atom - ✔✔What atom can lone pairs only be on?
linear - ✔✔What molecular geometry has two regions?
trigonal planar - ✔✔What molecular geometry has three regions?
tetrahedral - ✔✔What molecular geometry has four regions?
180 - ✔✔bond angle for linear
120 - ✔✔bond angle for trigonal planar
, <120 - ✔✔bond angle for trigonal planar w/ lone pair
109.5 - ✔✔bond angle for tetrahedral
<109.5 - ✔✔bond angle for tetrahedral w/ lone pair
<109.5 - ✔✔bond angle for tetrahedral w/ two lone pairs
Lewis dot structure - ✔✔diagrams that show the bonding between atoms of a
molecule and the lone pairs of electrons that may exist in the molecule
group number - ✔✔What gives the number of valence electrons?
central atom - ✔✔What part of the molecular structure is usually the least
Electronegative?
C, P, N, S - ✔✔What are the most common central atoms?
H, B, Be - ✔✔What three atoms do not have 8 electrons are them in the form of
bonds or lone pairs?
expanded octet - ✔✔- possible for elements in Period 3 or higher due to the
presence of the d orbital
- having more than 8 electrons
incomplete octet - ✔✔central atom is content with less than 8 electrons
