week 1 - atomic structure and EQ

• atoms basics

  • Mass number = no. of protons + no. of neutrons
  • number of protons = atomic number
  • electrons = protons

  A) mass number

  B) atomic number

  C) Z

  
• electrons

  • are distributed on different energy levels (ie. how close they are to atom's core)
  • no. of e- shells = its period number (which row)
• electron configuration

  • each shell is divided into subshells (ie. s,p,d,f) which is further divided into orbitals
  • each shell has its own energy level (1st shell has the lowest energy)
  • subshell: division within a shell, characterised by a specific shape
  • orbitals: regions within subshells where electrons can be found, having max. capacity of 2 e-

  A) 1

  B) 4

  
• orbital geometry

  • s: sphere (e- at centre of x,y,z axis)
  • p: dumbells (e-'s along x,y,z axes)

  
• bond energy

  • the energy required to overcome a bond

  A) hydrogen

  B) dipole dipole

  C) ionic

  
• electronegativity

  • a measure of how strongly an atom attracts electrons and form a bond
  • increases across a period as increased positive charge (protons) attracts e's more
  • decreases down a group as the number of shells increase, decreasing attraction to +ly charged protons

  A) ionic

  B) difference

  C) nonpolar

  D) polar

  
• geometry

  • 2s orbital of atom 1 and 2p orbitals of atom 2 should give 90 degree bond angle
  • but it gives 109.5, 120, 180
  • due to hybridization of orbitals

  A) 109.5

  
• lewis structures

  • 2 dots = one bond
  • in H2O, H has 2 valence e's, O has 6, so 2+6=8, hence H2O has 8 valence e's
  • e's leftover = lone pairs (non-bonding)
  • single e leftover = radicals

  
• formal charge formula (ie. atom charge)

  • = no. of valence e's - no. of lone pair e's - (no. of bonded e's)/2
  • no. of bonded e's = no. of bonds to the atom x 2

  A) 8

  B) 0

  C) +1

  
• resonance structures

  • applies to molecules with double/triple bonds
  • helps to show that molecules don't have a fixed arrangement of electrons but rather have a combination of multiple structures
  • eg. ozone (O3) does not have one fixed arrangement, rather, its electrons are able to move, hence the two possible structures

  
• resonance hybrids

  • a way to show the averaged or blended structure of a molecule, considering all resonance structures
  • the actual molecule is a blend/hybrid of all the resonance structures
  • delocalised e's: e's that are free to roam
  • (UNFINISHED/NOTUNDERSTOOD YET)
• molecular geometry

  • bonding pair: when an atom is bonded to another atom (single/double/triple bond is the same thing)
  • electron domain: includes bonding pairs and lone pairs around one atom

  A) trigonal planar

  B) tetrahedral

  C) trigonal planar

  
• Valence shell electron pair repulsion (VSEPR)

  • monash def: “Each group of valence electrons around an atom is located as far away from the others as possible to minimise repulsions ”
  • good def: electron pairs (bonding & lone) arrange themselves in a way that minimizes repulsion, leading to specific 3D shapes.
• VSEPR question

  • Boron has 3 valence e's, bonding with 3 F's it has a full valence shell, leaving no lone pair
  • Nitrogen has 5 valence e's, leaving a lone pair which repluses the hydrogens down

  A) planar

  B) pyramidal

  
• VSEPR question

  • last one: tanja said tetrahedral due to 2 lone pairs, google says bent/v-shaped

  A) trigonal planar

  B) linear

  C) tetrahedral

  D) pyramidal

  E) bent

  F)

  
• equilibrium

  A) reactants

  B) reactants

  C) products

  D) products

  E) reactants

  F) products

  
• Bronsted lowry acids/bases

  • only applies to scenarios with water

  A) conjugate base

  B) proton donor

  C) proton acceptor

  D) conjugate acid

  E) base

  F) lone pair

  
• acid base question

  A) base

  B) acid

  C) base

  D) acid

  
• strong/weak acids and bases

  • irreversible : full dissociation into ions
  • reversible: partial dissociation reaching an equilibrium

  A) strong

  B) weak

  
• pH, pOH and Kw

  • in pH, the H = H+ = H30+
  • Kw = equilibrium constant for the self-ionization of water, meaning the conc of hydronium and hydroxide ions is the same

  A) -

  B) -14

  
• formulas

  A) 14

  B) x

  C) +

  D) Kw

  E) 25

  F) +

  
• equilibrium and acid strength

  • dissociation constant = Ka
  • water is excluded in the denominator of Ka because its concentration is constant

  A) weak

  B) Ka

  C) small

  D) strong

  
• acid base graph

  • in the graph, the inflection point is where the concentrations of acid and bases are identical (in the buffering region)
  • the curve is consistent with a weak acid

  A) Ka
• Buffers

  • a solution that can resist changes in pH when an acid or base is added to it
  • usually a mixture of a weak acid and its conjugate base

  A) conjugate acid

  B) base

  
• Hendersson-Hasselbalch equation

  • applies only when in the buffer region

  A) conjugate base

  B) acid

  C) +

  
• calculating buffers

  • HCOOH is the acid, Na+COO- is the conjugate base

  A) 3.75

  B) 4

  C) -0.25

  
• blood buffer

  • blood's pH must be between 7.35 and 7.45 (narrow)

  A) H2CO3

  
• hybridisation

  • shows the hybridisation of carbon
  • it does this to FORM A SINGLE BOND (ie. sigma bond)
  • Eg. in methane, each of the four sp3 hybrid orbitals of carbon forms a sigma bond with a hydrogen atom

  A) 25

  B) 75