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Flashcards in Molecular polarity and IMF Deck (23):
1

2-atom molecules; how do you know if they are polar

  • if the 2 atoms are the same-nonpolar
  • if 2 atoms are different-look at electronegativity difference: if bond is polar, then molecule is polar. 

2

what is dipole

a dipole is a polar molecule

3

what is dipole moment

when you have unenven electron distribution. 

4

draw a polar molecule and its configuration, etc.

greatest electronegativity toward fluorine. If dipole moment is greater, electronegativity difference will be greater, and bigger the arror. 

5

how do you know if 3-atom molecules are polar? what are three things?

determine if the bonds are polar/nonpolar.

Molecules with one polar bond are always polar. 

If the central atom has a lone pair in 3 atom molecule, then it is polar. 

6

how to determine if "more than 3-atom molecules" are polar

see if central atom has lone pair: yes, then polar. 

if there are no lone pairs around central atom, and if central atom is bonded to same type of atom, if yes-nonpolar. 

If there is more than one central atom: look at each end seperately, polar and non polar ends can exist. 

7

What does IMF stand for and what is intramolecular forces? 

IMF is between what, what are the 2 types of attractive forces. 

intramolecular forces hold what in what structure, what involves intramoleculer forces, and it is stronger than what. 

IMF=intermolecular forces of attraction, between molecules. they are attractive forces either between 2 same types of polar molecules or 2 different types of polar molecules. 

Intramolecular forces hold atmos together in a molecule, chemical bonding involves intramolecular forces, much stronger than intermolecular forces. 

8

Describe energy in relation to IMF

to find out how strong each attraction is, we need to look at what? 

draw a diagram of H2O undergoing breakage of IMF and intramolecular forces of attraction. 

What can you conclude about BP, MP, evaporation rates. 

Are intramolecular forces stronger or weaker than intermoleculat forces? 

To find out how strong each attraction is, look at the amount of energy needed to break the attraction. 

SO if the greater the intramolecular and intermolecular forces, the higher the MP, BP, and much slower the evaporation rate. 

so intra molecular forces are much stronger than inter forces. 

9

what are the types of intermolecular forces, lets start with the dipole forces. 

Draw  a basic representation of dipole-dipole forces. 

dipole-dipole forces are attractive forces between what molecules. 

molecules will possess what. 

what is the dipole moment and what is the trend between dipole moment and the force of attraction. 

hydrogen bond, dipole-dipole, and dispersion forces are also called what? 

what does dipole stand for? dipole will only work for what? 

hydrogen bond, dipole-dipole forces and dispersion forces are called van der waals forces. 

polar molecule = dipole

it will only work for polar covalent molecules. 

attractive forces are between polar molecules. 

Molecules will possess a dipole moment (greater the difference in electroegativity). 

the large the dipole moment, the stronger the force of attraction between 2 molecules. 

H2O-H2

NH3-H2O

so these 2 are dipole-dipole forces. 

10

what are ion dipole forces. 

draw a diagram of ion-dipole fores between ions, and show which ones are stronger.

Do ion-dipole forces show Wan Der Waalls forces.

strength of attraction depends on what 2 factors?

cations are (big, small) than anions?

how do cations interact more strongly with dipoles.

what do you need to have the greatest interaction?   

ion dipole force is an attraction between an ion and dipole. 

cations are usually smaller than anions. so cation interacts more strongly with dipoles even if charge is same magnitude (1+ or 1-) because the charge is normally more concentrated in cation. 

 

So to have the greatest interaction, you need a very small cation and a very polar covalent molecule. 

ion-dipole forces are NOT Van der Wals forces

  1. strength of interaction depends on charge and size of ion. 
  2. & magnitude of dipole moment and the size of the polar molecule (greater, the size).
  3.  

11

what are dispersion forces. 

what is the trend in stronger the force of attraction. 

what is the trend in # of electrons. 

these exist in which molecules, and the ONLY forces in what molecules. 

DO they exist in ions. 

In what three cases, can these exist? 

 

what is polarizabiltiyy

what is the trend in number of elctrons, along with greater volume of electron cloud. 

when two atoms come close to each other : (just look at the image) 

they don't really exist in ions, but the ions can attract to dipole or induced dipole, forming an IMF.

these exist in ALL molecules, not ions, and the ONLY forces that exist in non-polar molecules.

the stronger the forces of attraction, the closer they want to be with each other.

more electrons, the more easily they are polarized.

polarizability is the ease with which electron distribution can be distorted. 

normally the larger the number of electrons and greater volume of electron cloud, more easily polarized. 

the 3 cases:

  • dipole-induced (temporarily) dipole
  • induced dipole-induced dipole
  • ion-induced dipole

 

12

What is the hydrogen bond. 

is it exactly a chemical bond. 

what do you MUST have, and what are the three other critical elements.

it occurs between what in a polar bond?? 

You MUST have hydrogen, then Oxygen or Nitrogen or Fluorine. 

it is a special type of dipole-dipole force. and occurs between H atom in a polar bond (N-H, O-H, and F-H) and electronegative O,F,N atom. 

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