Midterm Topics: Chemistry of LIfe

Question 1

What are ions? How do they differ from atoms?

Answer 1

• Ions: charged particles that form when atoms gain or lose electrons
• Atoms: smallest, most fundamental unit of matter that retains the properties of an element
• Ions are essentially charged atoms, can be negative or positive

Question 2

How can you tell if an atoms is reactive?

Answer 2

• At baseline they are neutral, but they become reactive if their valence shell isn’t full
• Less full shell=more reactive

Question 3

What is the octect rule?

Answer 3

Elements will combine 8 electrons in valence shell

Question 4

What are covalent bonds; polar and nonpolar?

Answer 4

• Covalent Bonds: Involve sharing of electrons, each electron is attracted to the other atoms nucleus
• Polar Covalent Bonds:
  
  • Unequal sharing of electrons
  • Occurs when 2 atoms differ in
    electronegativity
  • Partical charges exist around the
    atom within the molecule
• Non-Polar:
  
  • Equal Sharing of electrons
  • Occurs when 2 atoms have similar
    electronegativity
  • No charges present

Question 5

What is polarity based on?

Answer 5

Based on charge distribution. It is the result of uneven partical charge distribution

Question 6

What are ionic bonds; hydrogen bonds; hydrophobic interactions?

Answer 6

• Ionic Bonds: non-covalent bond, forms when 2 ions of opposite charges are attracted to each other
• Hydrophobic Interactions: non-polar molecules will tend to associate with each other when in a polar solvent like water
• Hydrogen Bonds: Occurs between…
  • Hydrogen with a partical (+) charge
    - Another atoms with a partical (-)
    charge (often O or N) or a fully (-)
    charge

Question 7

What bonds are the strongest and the weakest?

Answer 7

Strong: Covalent Bond
Weak: Hydrogen bond

Question 8

What is electronegativity? Based on?

Answer 8

• Electronegativity tendency of an atom to attract electrons
• Based on.. 1. occupation of valence shell (closer to being filled = more electronegative) 2. Distance from nucleus (closer the valence shell is to the nucleus the more electronegative)

Question 9

What is pH?

Answer 9

• A measure of concentration
• Low number (1,2)= acidic; high concentration of free protons
• Hugh number (11,12)- basic; low concentration of free protons