1. Shape and Drawing ; Bonding-Hybridization and Bonding-Resonance Flashcards
what are Lewis structures and why are they important?
-diagrams that represent the valence electrons of atoms within a molecule
-help determine molecular shape
what are the steps to draw a Lewis structure?
- find the total number of valence electrons
- put the least electronegative atom in the middle
- form electrons between atoms
- fulfill the octet rule
- move electrons from outer atoms to inner atoms to help fulfill the octet rule
what is the trend of electronegativity on the periodic table?
less electronegativity moving from right to left or down a collumn
what is the formula to find the formal charge?
FC=# of valence electrons - (lone pairs + # of bonds)
how many bonds does hydrogen make?
one
how many bonds does Boron make?
three
which atom mainly makes five bonds?
phosphorus
which atom mainly makes six bonds?
sulphur
what is a trick to remember the number of bonds an atom typically makes?
the ones digit in the number above the column
what are the models to explain chemical bonds? (5)
Lewis dot structure, valence shell electron repulsion theory, valence bond theory, hybridization, molecular orbital theory
what is the angle of a linear molecular shape?
180
what is the angle of a trigonal planar molecular shape?
120
what is the angle of a tetrahedral molecular shape?
109.5
what is the angle of a trigonal bipyramidal molecular shape?
120 and 90
what is the angle of an octahedral molecular shape?
90
how is the valence bond theory distinct from the other chemical bond models?
shows how the overlap of incompletely filled atomic orbitals forms bonds
how many pi bonds are in a triple bond?
two
what do sigma bonds and lone pairs require?
sp hybridized orbitals
what is a sigma bond?
a single bond
what happens to the strength of a bond if the bond length increases?
the bond strenth decreases
what is a delocalized system?
a molecule where its lone pairs and multiple bonds can be moved
what is a resonance structure?
when a molecule can be represented using two or more other structures
what are the characteristics of better resonance structures? (4)
-has more bonds
-does not violate the octet rule
-fewer formal charges
-charges correctly distributed according to electronegativity
how is the VESPR theory distinct from the other chemical bond models?
emphasizes that regions of negative charge will repel each other creating a shape used to predict hybridization
why are imperfect angles formed?
-when a less-than-ideal geometry is formed because of the presence of a ring
-repulsion of electron lone pairs
what are polar bonds? (2)
-if there is a bond between two electrons, one atom in the bond is more electronegative than the other
-electronegativity difference greater than 0.4
what are the characteristics of polar molecules?
-at least one polar bond
-appropriate geometry
what are intermolecular forces?
the attractive and repulsive forces within a molecule
when do dipole moments cancel out?
if two dipole arrows are perfectly opposite from one another
why are intermolecular forces considered?
to get a sense of a molecule’s boiling and melting point
what are the intermolecular forces listed from weakest to strongest?
Van Der Waals, dipole dipole, hydrogen bond, ionic bond
what does a bigger molecule with more atoms do to the melting or boiling point?
increases it
what does a strong intermolecular force do to the boiling or melting point?
increases it
what does a branched molecule do to the melting or boiling point?
decreases it
how is the molecular orbital theory distinct from the other chemical bond models?
two atomic orbitals interacting to make a bond
