InChem foundation

What does the plum pudding model look like and consist of?

Positive mass with small, negative electrons embedded

What does the Rutherford atom look like and consist of?

Positive nucleus with negative electrons orbiting nucleus

What is the problem with the Rutherford atom?

All electrons are equal contradicting idea of atomic emission spectra

What is the atomic emission spectra?

When atoms are given a lot of energy & light is emitted

What is the Bohr atom?

Same as Rutherford atom but electrons are at different distances from the nucleus

How much energy do electrons closer to the nucleus have?

More stable & lower energy since they are more tightly bound

What are transitions?

When electrons absorb energy and it moves from a lower energy level (ground state) to a higher energy level (excited state)1

What do emission lines represent?

Energy levels in atom

What is the formula of showing energy in a quantum level?

En = k / n2

n = Quantum number e.g n=1 etc

k = Plancks constant

What is the problem with the atomic emission spectra?

-Works for hydrogen, but not for heavy atoms

• Doesn't explain periodic properties

-Bohr model doesn't explain everything

What is the deviation for De Broglie's equation?

What is the wave particle duality?

Subatomic particles can act as both particles & waves (electrons can diffract)

What is Heisenberg's uncertainty principle?

Uncertainty associated with momentum

Why is uncertainty associated with momentum

To see electron, light waves reflect from spherical electron & meets eye

• Light wave adds energy & changes momentum of electron

What is the problem with Bohr's atom?

Shows orbit which gives electron well defined orbit, however electrons do not exist in orbits

What is used instead of orbits?

Orbitals = Area of space around the nucleus where electrons are seen (probability distributions)

Why must wavelengths be in integral number when electron moves in circular manner?

Destructive interference may occur (λ n = 2 pi r)

What is schrodingers equation?

Describes how wave function evolves overtime?

What does the wave function describe?

Amplitude of x, y or z (only applies to ELECTRONS)

What does wave function^2 represent?

Probability density

What are the components of wave function?

Wave function = Rn1 (r) x Y 1 m1

n1 & m1 = Quantum numbers

Y = Angular wave function (Direction)

What is the n (principal) quantum number?

Includes positive integer values (0 not included)

e.g = n=1 ,2,3,4 etc

What does n (principal) quantum number determine?

Size of orbital therefore energy

What is L (Azimuthal) quantum number?

-Known as angular momentum

Includes positive integer values (0 included) up to a max of n -1

e.g = n=4 L can be 0,1,2 or 3

What does L (Azimuthal) quantum number determine?

Affects shape so no changes in energy

What is the mL quantum number?

-Known as magnetic quantum number

-Includes positive integer values (0 included) between -L & +L values

e.g = At L=2 can be -2,-1, 0 ,1,2

What does mL quantum number determine?

Orientation of orbital

How do you name orbitals?

L = 0 -> S

L = 1 -> p

L = 2 -> d

L= 3 -> f

L = 4 -> g

-Letter code preceded by principal quantum number e.g n=3 & L=1 so 3p orbital

What is the radial wavefunction?

R = Function of distance from nucleus (r)

-R never goes to 0 as r -> infinity

What is the Bohr radius?

Probable distance of electron from nucleus for H atom in ground state

What is irrelevant for negative values of R?

-Electron probability as square of negative values give out positive

-Not relevant to electrostatic charges

What is negative values of R important for?

Bonding

What are radial distribution functions (RDF)?

Total probability electron will be found at given distances from nucleus regardless of electron

What are the limitations of using wavefunction^2?

Only gives probability of finding electron at a single point

How do you find RDF?

Probability of electron being at r x number of locations at r

What happens if n (orbital size & energy) increases?

Area of max probability (density) increases

What is boundary surface?

Where there is 90% probability of finding an electron.

When is boundary surface used?

When there is a small probability of finding an electron far away from nucleus

What are radial nodes?

Distances with 0 probability

How do you find number of radial nodes?

n - L -1

What is angular wavefunction dependent on?

L & ml only (no n)

What shape do ns orbitals give off?

Spherical shape

What is L=0 (ml 0) name?

ns (s orbitals)

What is L=1 (ml can be -1,0,+1) name?

np orbitals (p orbitals)

What shape do np orbitals give off?

Dumbell shape

What is l=3 (ml -3,-2,-1,0,1,2,3) name?

nf (f orbitals)

What shape is nf orbitals?

A lot more angular nodes

What are angular nodes?

Planes with 0 electron probability

What are orbital shapes independent of?

n (orbital size)

What is l=2 (ml is -2,-1,0,1,2) name?

nd (d orbital)

What shape is nd orbitals?

What does V (potential energy) in Schrodingers equation include?

Sum of electron attraction & repulsion

Why can Schrodingers equation only be applied to the H atom and carbocations with 1 electron?

No electron repulsion in H atom (1 electron only)

Why can't Schrodingers equation be applied to atoms with more than one atom?

Location of electrons must be seen for atoms with more than one electron

How do you make it so Schrodingers equation can be used for atoms with more than one electron?

-Use H atom (or carbocations with one electron) as all orbitals have similar shapes

-Orbital energies vary depending on effective nuclear charge

What quantum number(s) do orbital energies depend on now for atoms with more than one electron?

n & l (energy, size & shape)

Why do electrons in orbitals with larger n quantum number have higher energy?

They have probability distribution further from the nucleus & experience less nuclear charge so are less tightly bound

Why do electrons in orbitals with smaller n quantum number have lower energy?

Lower probability distribution from nucleus & experience greater nuclear charge so are more tightly bound

What is the shielding effect?

When outer electrons feel lower effective nuclear charge so have higher energy

Why is s<p<d<f in terms of energies?

-In RDF graph, 2s has a residual maximum (2 peaks)

-So 2s penetrates closer to nucleus than 2p electrons so experiences greater nuclear charge

Why do orbital energies decrease with increasing Z (atomic number)?

Electrostatic attraction of electron increases

Why does 4s become more penetrating for K & Ca?

As Z increases, 4s becomes more penetrating

-> Stronger nuclear charge = Energy decreases

What is electron penetration?

How close an electron can get to the nucleus

Why does 3d have lower energy than 4s from Sc onwards?

Sufficient electrons

What is the Afbau principle?

"Add 1 proton, 1 electron & some neutrons to orbital of LOWEST ENERGY available"

What is ms quantum number?

Spin quantum number

-> Have values of +1/2 or -1/2

What is Pauli exclusion principle?

No 2 electrons in any system can have identical values for all FOUR quantum numbers

-> Values of ms must be different (Must have opposite spins)

What is Hund's rule?

Most stable state is one with identical or parallel spins

->Otherwise repulsion between electrons may occur

What are valence electrons?

Incomplete orbitals with higher energy & are affected by chemical reactions

What are core electrons?

All orbitals with specific quantum number are full

-> e.g = 1s2 for He to F

Why are full & half filled shells more stable in neutral atoms?

Electron repulsion is minmised

What is periodicity?

Similar chemical properties

Why does periodicity occur?

Valence orbitals

How does electron fill for transition metals?

4s always empties before 3d

Who first drafted the periodic table?

Mendeleev

What did Mendeleev do?

Ordered periodic table by increasing atomic weights (relative atomic masses)

What did Mosely discover?

Periodic table instead ordered by increasing atomic numbers -> Defines periodic table

What is the structure of the periodic table?

ns2 np6 = Noble gases -> fully filled shells

ns1 = Group 1

ns2 = Group 2

ns2 np5 = Group 17 metals

ns2 np4 = Group 16 metals

ns2 np3 = Group 5 metals

What are the main group elements?

• s- block -> groups 1&2

-p- block -> groups 13-18

What are transition elements?

Incomplete d-orbitals is either metal, compound or complex

What are NOT transition metals?

Zn, Cd & Hs

What are actinides or actinoids?

Partially filled 5f orbitals

What are lathanides or lathanoids?

Partially filled 4f orbitals

What are some multi-electron system rules?

-Same quantum numbers as hydrogen

-Same angular functions as hydrogen

-Radial functions similar to hydrogen, but contracted of increased nuclear charge

Why are electrons placed far apart as possible?

Minimizes colombic (electrostatic) repulsion

Are parallel spins in an electron more unstable or stable?

Stable

What is the formula for electron energies in multi-electron systems?

E = -Rn hc Z^2 / n^2

What is the effective nuclear charge?

Electron experiences less nuclear charge than full nuclear charge because of shielding

What does shielding from other electrons depend on?

n (principal quantum number)

What does penetration refer to?

Electron density. Electrons in orbitals have different wavefunctions and RDF

Why does 2s get filled before 2p?

-2p has no radial node

-2s is less shielded of radial node so experiences greater nuclear charge & lower energy

So 1s shields 2p more than 2s

Why is 4s filled before 3d?

-4s has 3 radial nodes (n-L-1)

-3d max closer to nucleus than 4s

What does effective nuclear charge depend on?

Which shell electron is in -> Valence electrons in 3s experiences smaller nuclear charge than 1s of shielding

What is Slater's rules?

Effective nuclear charge (Zeff) = Z - S

-Z = Actual nuclear charge

-S = Shielding constant

Why doesn't perfect shielding exist?

-Electrons with same n contribute to 0.35 to s (shielding constant) ->Not much

-Electrons with 1 below n contribute to 0.85 to s -> Better shielding

-Electrons with low n contribute 1 to s -> Perfect shielding

What is ionisation energy?

Sufficient energy required to detach one or more electrons from a gaseous atom, molecule or ion to form one gaseous ion

Are ionisation energies always positive?

Yes

What happens to energy required for second,third,fourth etc ionisation energies?

Increases each time

What are the general trends for first ionisation energy?

-General increases across period

-General decreases down the group

Why does first ionisation energy decrease down a group?

Increasing principal quantum number, energy required to remove electron decreases. However, no dramatic decrease of shielding