SHAPES OF MOLECULE Flashcards
CH4 SHAPE AND BOND ANGLE
Tetrahedral
109.5
NH3 SHAPE AND BOND ANGLE
pyramidal
107
H20 SHAPE AND BOND ANGLE
Bent
104.5
BF3 SHAPE AND BOND ANGLE
trigonal planar
120
ELECTRONEGATIVITY DIFFERENCE OF A COVALENT BOND
0
ELECTRONEGATIVITY DIFFERENCE OF A POLAR COVALENT BOND
0 - 1.8
ELECTRONEGATIVITY DIFFERENCE OF AN IONIC BOND
more than 1.8
WHAT MAKES A BOND POLAR
when the bonded atoms have a different electronegativity value therefore the bonded electron pair is shared unequally
WHAT IS A DIPOLE
the separation of opposite charges
WHAT ARE INTERMOLECULAR FORCES and what is the order of strength
AND THE THREE CATEGORIES
weak interactions between dipoles of different molecules
London forces
Permanent dipole dipole interactions
Hydrogen bonding
What is electronegativity
the ability for an atom to attract electrons towards itself in a covalent bond
2 examples of polar covalent bonds
H-Cl H-O-H
Why is CO2 not polar
as it has 2 polar bonds that are arranged symmetrically so no overall polarity
What is an induced dipole-dipole
a temporary dipole created when atoms or molecules are near each other so electrons can move from one end to another
How are crystal structures held together
Induced dipole-dipole forces hold molecules together,(covalent bonds hold the atoms together)
What happens when you boil a liquid
You break the weak induced dipole-dipole forces, NOT THE COVALENT BONDS
difference of boiling points of straight chain hydrocarbons and branched hydrocarbons
Straight chain hydrocarbons can pack together tighter, therefore there are more stronger induced dipole-dipole forces so the boiling point is high
Branched hydrocarbons cant pack together as close therefore the induced dipole-dipole forces are weaker and boiling point is therefore lower
What is a dipole-dipole force
weak electrostatic force that exists between molecules with polarity
What is a test for polar molecules
run a steady stream of the liquid near a charged rod, the liquid will bend towards the rod if polar as the molecules align to face the rod
When does hydrogen bonding occur
when hydrogen on one molecule forms a bond with the lone pair on either nitrogen, oxygen or fluorine as they are very electronegative
Trend in boiling points of hydrogen halides
HF, HI, HBr, HCl
HF has hydrogen bonding so will need the most energy to overcome the electrostatic forces, the other 3 do not, so as the mass of the molecule increases, so does the size of the electron cloud, and so more induced dipole-dipole forces
