Lecture 1 book recap Flashcards
(32 cards)
how do you calculate the dipole moment?
the size of the charge x the distances between the charges with a si unit of D (debye) which is to the power of -18
1A is = to
1 x 10^-8
what are electrostatic potential maps
it is a model that shows how charge is distributed in the molecule under a map and therefore shows to which degree a molecule attracts the other molecules
what do the colours on the electrostatic map show
red signifies the region with the most negative electrostatic potential
Blue signifies the region with the most positive electrostatic potential
then from orange to yellow to green is the middle between red and blue from orange being more negative the yellow and green
the size of the electrostatic potential map shows?
the electron denisty of the molecule
formal charge =
number of valence electrons - (number of bonds + number of lone pairs)
what is the probability of finding the electron in 2s orbital
usually, it would be more than 90% but due to the wave-like property of the electron it will form a standing wave with nodes and anti-nodes where the anti-nodes would have a probability of zero to find it
when two orbitals join in a sigma bond what happens to the energy
energy is released as the electrons in the orbitals are attracted to their own nucleus and to the nucleus of the other orbital
what is bond dissociation energy
the energy required to break a bond, or the energy released when the bond is broken
(very covalent bond has a specific bond length and bond dissociation energy)
when two orbitals form a sigma bond they form a new molecular orbital, and that is due to?
the wave-like behavior of electrons the two orbitals can constructively interfere.
The constructive combination of two s atomic orbitals is called a
a sigma bonding molecular orbital
The destructive combination
of two s atomic orbitals is called
S* antibonding molecular orbital where to reaction happens
what binds the molecular orbitals
the electrons in the middle between the two nuclei can freely attract both nuclei, and this increase in electron density and keeps the nucleus bonded and have low energy making it stable
how do some molecular orbitals not bond
because the electrons are not found anywhere between the nuclei because of the nodal plane, this leaves the positive nuclei exposed to each other causing them to repulse each other and have very high energies making it unstable
the covalent bond strength increases as the
as the atomic orbital overlap increases
what is a sideway deconstructive overlap between two p orbitals
pi* antibonding molecular orbital which has two nodal planes
which is stronger C=C or C-C
C=C
where are the high electron density regions in ethyne C≡C and why
in the front, back, top, and bottom of the molecule as the two unhybridized orbitals are perpendicular to each other (to minimize repulsion) so they side way overlap
which is stronger C≡C or C=C
C≡C because it is held by 6 electrons
what are the three reasons carbon might form 3 bonds
- it has a positive charge (it forms 3 hybridized orbitals of 1 s and 2 p forming 3 covalent bond with the 3rd p being empty and perpendicular
- it has a negative charge (it forms 3 hybridized orbitals of 1 s and 2 p forming 3 covalent bonds with the p orbital have an unpaired electron whose electron density is split between the two lobs (50%-50%)
- It has one unpaired electron (radical) (it forms 4 hybridized orbital os 1s and 3 p with 3sp^3 forming bonds with hydrogen and one sp^3 having a lone pair causing all the orbital to move very far away from it to form an angle of 107.3 trigonal pyramidal)
how does Nitrogen form 3 bonds
nitrogen has 3 lone pairs in its p orbital which can explain how it forms 3 covalent bonds which should form 90* but when observed ammonia forms a bond angle of 107.3 which can only be explained by the fact that ammonia has 4 hybridized sp^3 orbital at which 3 of of them form covalent bonds and one of them would have a lone pair which has a larger election density than the rest of the sp^3 orbitals (when the join with hydrogen) so they are used to an angle of 107.3
ammonium ion forms a bond angle of
109.5 because all the N-H bonds are the same and there are no lone pairs
how does oxygen form 2 bonds
oxygen has two lone electrons in its valence shell so it is expected that it forms two covalent bonds but from data, we see that water has an angle of 104.5 and that can be explained by the formation of 4 hybridized orbitals of sp^3 with 2 having one election and being used for bonds and the other two having a lone pair in there sp^3 orbital and this causing so much repulsion forming the bond angle of 104.5 (v-shaped)
what is bonding like in HX
so halides have only one lone electron in their valence shell so it forms only one bond so due to that we can figure out the bond angle it forms but we do know that the 3 lone pairs of electrons are very energetically similar and want tp minimize repulsion which indicates that X forms 4 hybridized sp^3 orbitals with 3 of them having a lone pair and one of then having an electron reading for covalent bonding so HX is due to the overlap of 1sp^3 and s from hydrogen
