CHEM111 midsem test

Cathode ray tube experiment

JJ Thomson- discovered electrons and charge/mass ratio

Oil drop experiment

RA Milikan- measured charge of electron

Ernest Rutherford experiment

shot alpha particles at thin gold foil- discovered the nucleus

who discovered the neutron?

James Chadwick

quantum numbers- n

principal quantum number
n=0,1,2… infinity

determines energy and orbital radius

quantum numbers- l

orbital quantum number

l=0,1,…n-1

determines shape and name (s,p,d,f)

quantum numbers- ml

magnetic quantum number

ml= -l,…0,…+l

determines orientation/number of each type of orbital

shell

electrons with same value of n

subshell

electrons with same value of n and l

orbital

electrons with same value of n, l and ml (2 per orbital)

isotope

equal number of protons, different number of neutrons= different mass number

2p orbital lobes/nodal planes

two lobes and one nodal plane

3d orbital lobes/nodal planes

four lobes and two nodal planes

Aufbau principle

electrons occupy the lowest-energy orbitals first

Pauli exclusion principle

each orbital can accommodate two electrons with opposite spins

Hund’s rule

most stable electron arrangement within orbital level has the greatest number of parallel spins

mass of atomic particles in order

electron < proton < neutron

Chromium special case

4s1,3d5

Copper special case

4s1,3d10

ionisation energy

energy required to remove an electron from a gaseous atom to form a positive ion

first ionisation energy increases as…

you go up and across periodic table

Zeff

effective nuclear charge- The actual charge felt by a valence electron after accounting for the shielding caused by inner electrons. 

Zeff= number of protons (atomic number) - number of shielding electrons

As atomic radius decreases, Zeff…

increases

electron affinity

positive energy change that occurs when electron is added to an atom (energy released)

electron gain energy

-electron affinity

electronegativity

Linus Pauling- an atoms tendency to attract electrons to itself
increases up and across periodic table

van Arkel diagram uses electronegativity values of elements to predict…

type of bonding

ionic solids

lattice of cations and anions- electrostatic bonds means high melting points, can conduct when molten

metallic bonding

lattice of atoms surrounded by a delocalised sea of electrons- variable melting points

covalent bonding

sharing of electron pairs, entire solid is a giant molecule eg silicon

molecular bonding

covalent bonds between atoms, weak intermolecular bonds between molecules eg iodine

incomplete octet examples

boron- only needs 6 valence e-s to be stable

beryllium- only needs 4 valence e-s to be stable

hypervalent atoms

sulfur- 12 valence e-s

phosphorus- 10 valence e-s

Charles law

V1/T1=V2/T2
volume is proportional to temp at constant pressure and mols

combined gas law

(P1V1)/T1 = (P2V2)/T2

Dalton’s law

P total= sum of all partial pressures (non reacting gases)

Boyle’s law

P1V1=P2V2
volume is inversely proportional to pressure

constant n and t

avogadros law

V1/n1 = V2/n2

constant pressure and temp

why is CO2 a greenhouse gas?

as it vibrates it absorbs and re emits infrared energy back into atmosphere, some of it towards earths surface

what makes an ozone depleting gas?

they release a radical when C-X bond is broken by uv radiation
eg Br, Cl

what makes a molecule flammable?

C-H bonds, products are H2O, CO2, sometimes NO and SO (acid rain)

linear

2 bonded pairs, no lone pairs
bond angle 180

Trigonal planar

3 bonded pairs, no lone pairs
bond angle 120

tetrahedral

4 bonded pairs, no lone pairs

bond angle 109.5

trigonal bipyramidal

5 bonded pairs, no lone pairs
bond angle 90 and 120

octahedral

6 bonded pairs, no lone pairs

bond angle 90

trigonal pyramid

3 bonded pairs, 1 lone pair

bond angle 106.7

bent

2 bonded pairs, 2 lone pairs

bond angle 104.5

bond angle decreases as..

number of lone pairs increases

state functions

P, T, V, n

heat

q, transfer of energy due to difference in temperature

unit - joules