Structure and Bonding Flashcards
How can we rank different ionic compounds based on their melting points ?
Ionic bonds are formed through Coulomb’s Force between anion and cation - thus the smaller the radius the stronger the force thus higher melting point
What determines if the bond between 2 atom is going to be ionic or covalent ?
Electronegativity difference - reference 1.9
Which molecules will orient themselves in an electric field ?
Molecules that have a permanent dipole moment
What shows charge distribution in a molecule ?
Electrostatic potential maps
Difference between polar and nonpolar in terms of EN ?
EN less than 0.5 will not form charge difference thus no permanent dipole moment = nonpolar molecule
How does Resonance structures differ ?
They only differ by the electron distribution, the connectivity is the same
Which resonance structure exist in real life ?
None of them. Its the average of the structures
Bond order
butun resonance structure topluyorsun specific hangi bond ise sonra resonance structure sayisina boluyorsun
How to assign formal charges ?
Valance electron sayisi - etrafindaki electron sayisi
VSEPR Theory
predicts bond angle - shape
Is a tetrahedral structure polar or nonpolar ?
A2B2
The ones in the same plane can cancel out but you can not cancel the other 2 because they can never be in the same plane - thus nonpolar
Why water is polar ?
Because EN difference is not 0 thus it has a dipole moment
What does it mean “ intermolecular forces” ?
between molecules - affects physical properties
What affects the degree of dispersion forces (London forces) ?
Surface area of the molecule
in other words larger electron density = larger dispersion forces
also momentary not continuous
Hydrogen interaction between what and what
The lone pair on the oxygen and hydrogen on another molecule
attention!! - intermolecular forces
How many hydrogen bonding in a water molecule ?
4
Why C-H bonds cannot participate in hydrogen bonding ?
Because C-H bonds are not polar enough - EN difference
What happens to the number of hydrogen bonds in a water molecule as it changes phases from gas to liquid ?
Becoming stronger thus more hydrogen bonds
what does VBT answer ?
Focuses on atoms instead of molecules - also to explain bond angles
sigma bond
the overlap of 2 orbitals are on the axis
what happens after the overlap of 2 orbitals ?
the electrons are LOCALIZED between the 2 nuclei - restricted to an area
hybridization ?
mixing of orbitals in the same atom
what does hybridization explain in VBT?
it explains bond angles in the orbital level - localized approach
what does the number of electron density decide ?
for example - tetrahedral electronic arrangement !!!
SHAPE DOES NOT MATTER IN VBT
if electron density = 4
tetrahedral electron arrangement
109.5
sp3d hybridization
5 regions of electron density - trigonal bipyramidal electron arrangement - 90, 120, 180
pi bond overlaps where ?
sideways - they are 90 degree to the plane
how to count pi bonds ?
4 lobes - 2 overlap with each other on 2 sides but only forms 1 pi bond
molecular orbital theory
describes bonding in terms of molecular orbitals that are formed by combining atomic orbitals
-also explains paramagnetism, diamagnetism
paramagnetic molecules
at least 1 unpaired electron
diamagnetic molecules
no unpaired electrons
which one creates a node ?
bonding orbital or antibonding orbital
antibonding orbitals create a new node between the 2 nuclei oyuzden adi antibonding
which one higher energy bonding or antibonding orbital ?
antibonding because its trying to deconstruct the bond
Filling the elecrons from what to what MOT ?
from lowest energy to higher from bonding to antibonding
Why there is no 2px pi bond ?
Because its a bond on the axis thus thats the definition of a sigma bond
Bond order in MOT
bonding electrons - nonbonding electrons /2
