intro to chem

Question 1

what is an atom / element

Answer 1

• comprised of sub-atomic particles
• dense nucleus of protons (+) and neutrons (=)
• orbiting distant electrons (-), in shells / energy levels, valence orbit (highest energy), valence electrons (interact with other electrons / atoms)
• set number of protons / neutrons
• atomic number = number of protons or electrons (same)
• atomic mass (protons + neutrons)
• uncharged atom = number of protons = electrons

Question 2

what is potential energy in relation to orbits

Answer 2

• attraction between electrons and nucleus = energy needed to keep them in orbit
• potential energy due to electrons relative position
• electrons represent energy stores for atoms, have the potential to form bonds etc

Question 3

what are charged ions

Answer 3

• number of electrons does not equal protons
• cations (+)
• anions (-)

Question 4

describe how outer electrons are more reactive

Answer 4

• outer energy level = maximum of 8 electrons
• octet rule: atoms tend to establish completely full outer energy shells
• inert: possess full complement of electrons in outer cell (noble gases)
• reactive: atoms lacking a full complement of electrons (tend to form bonds and gain / lose electrons to fill outer shell)

Question 5

briefly describe the functional groups of organic chem

Answer 5

• alcohol: hydroxyl (OH), polar, forms H bonds
• aldehyde: carbonyl (H double bonded O), polar, end chain
• ketone: carbonyl (C double boned O), polar, middle chain
• carboxylic acid: carboxyl (COOH), loses proton in water to become (COO)
• amine: amino (NH2), in water accepts proton to become (NH3)
• amide: amino (C double O NH2), polar, uncharged
• thiol: thiol (CSH), found on some AA
• phosphate: phosphoric (COP(OH2)O)

Question 6

what are the different types of bonding

Answer 6

• ionic: attraction between atoms with opposite electrical charges (ions), TRANSFER of electrons
• covalent: between atoms that SHARE one or more pairs of valence electrons, strength depends on # shared electrons, strong
• hydrogen: difference in polarity, opposites attract, attraction between H and FON of other molecule, weak, transient, enormous net effect

Question 7

why is water important

Answer 7

• exists as a liquid under most conditions on earth, ideal medium for life
• hydrogen bonding, good solvent, heat storage, high surface tension

Question 8

describe the chemistry of water

Answer 8

• oxygen covalently bonded to 2 hydrogen atoms
• attract shared electrons in covalent bonds
• shared electrons = near oxygen (more electronegative)
• electronegativity: attraction an atom has for covalent electrons
• polar: distinct ends with partial charges

Question 9

what is polarity

Answer 9

• non polar (evenly distributed)
• polar (unevenly distributed, partial charges present)
• like dissolves like etc

Question 10

what are acids and bases

Answer 10

• ionisation of water, spontaneous ion formation H20 to H + OH
• acids: dissociate in water, increase H conc. (HCl - H + Cl)
• bases: accept H when in water, (NaOH - Na + OH - OH + H - H2O)

Question 11

what is pH

Answer 11

• measurement of H ions

- negative logarithm (0-14) where 0 = acidic, 14 = basic, 7 = neutral

Question 12

what are buffers

Answer 12

• substance that acts as a reservoir for H ions, donates H when pH rises, removes H when pH falls, constant pH
• mammalian blood buffer (CO2 + H2O H2CO3 HCO3- + H+)