Fundamentals of Biochem II

Question 1

What are the two intramolecular forces of attraction?

Answer 1

Ionic and covalent bonds

Question 2

What are ionic bonds?

Answer 2

• Bonds between oppositely charged atoms (when an anion and cation bond)
• Relatively weaker bonds especially when in solutions

Question 3

What are covalent bonds?
(More important in bio)

Answer 3

• They arise from the simultaneous attraction of 2 nuclei for a shared pair of electrons; it occurs between 2 non-metals
• Relatively stronger bonds

Question 4

What is electronegativity?

Answer 4

• The measure of an atom’s ability to attract shared electron pairs

Question 5

What is En?

Answer 5

• An atoms electronegativity number
• It indicates the strength at which an atom attracts electron pairs

Question 6

What is △En?

Answer 6

• The electronegativity difference between two atoms

Question 7

What is polarity?

Answer 7

• When electron pairs are unequally shared
• One atom takes on a partially positive charge (𝛅+), and one takes on a partially negative charge (𝛅-)

Question 8

What is 𝛅/delta?

Answer 8

• It is used to show a particle or relative charge on one end of a bond

Question 9

Important note about polarity

Answer 9

There is a difference between polar bonds and polar molecules

Question 10

The bond is non-polar covalent if….

Answer 10

The △En is zero

Question 11

The bond is polar covalent if…

Answer 11

The △En is greater then zero but less than 1.7

Question 12

The bond is polar ionic if…

Answer 12

The △En is greater than 1.7-4.2

Question 13

What is hybridization?

Answer 13

• The process of overlapping valence electrons

Question 14

What are non-bonding/lone pairs?

Answer 14

• Electrons which orbit around atoms but do not take place in bonding within a covalent compound

Question 15

Do non-bonding/lone pairs take up more or less space than bonding pairs? why?

Answer 15

• They take up more space than bonding pairs do
• They end up repelling and compressing bond angles of bonding pairs, this makes the molecules 3D

Question 16

Why is H2O so important to living things?

Answer 16

• Living things are mostly H20 which is polar, so polar substances pass through the body faster

Question 17

What are the 3 major types of intermolecular forces?

Answer 17

• London forces
• Dipole-dipole forces
• Hydrogen bonds

Question 18

London Forces

Answer 18

• Weakest intermolecular forces
• Occurs between all molecules
• A temporary attractive force
• Cause non polar substances to condense to liquids and to freeze into solids when the temperature is lowered enough

Question 19

How do London forces occur?

Answer 19

• They result from the temporary displacement of the electrons around the atoms
• The strength of London force tends to increase with increasing molecular mass since there are more electrons

Question 20

Dipole-dipole Forces

Answer 20

• Medium strength forces
• Between polar molecules
• special conditions

Question 21

How do dipole-dipole forces occur?

Answer 21

• Occurs between molecules that have permanent net dipoles
• The partial positive charge on one molecule is electrostatically attracted to the partial negative charge on a neighbouring molecule

Question 22

Hydrogen Bonds

Answer 22

• Strongest intermolecular force
• Occurs when Hydrogen bonds with Nitrogen, Oxygen and Fluorine
• special conditions

Question 23

How do hydrogen bonds occur?

Answer 23

• They occur between molecules that have a permanent net dipole resulting from hydrogen being covalently bonded to either fluorine, oxygen or nitrogen

Question 24

Factors that affect molecular shape

Answer 24

• electronegativity
• polarity
• hybridization
• nonbonding/lone pairs