2 atomic structure Flashcards
structure of an atom
positively charged nucleus
‘cloud’ of negative charge
electrostatic attraction betw pos nucleus and neg charged electrons – holds it tgt
define isotope
different atoms of the same element
same protons
but diff number of neutrons
speed of light? (in section 2 of data booklet)
3.00 x 10^8 m/s
excited state electrons are further / closer to the nucleus
further (higher energy level)
in a line emission spectrum of hydrogen, describe the lines
they get closer toegther towards the blue end of the spectrum (convergence towards the higher energy end)
what does it mean when lines converge towards the higher energy end in an emission spectrum
the electron is reaching its maximum amt of energy = ionisation energy of the electron
who observed line emission spectra
Johannes Balmer
(the balmer series is in the visible spectrum)
lines in an emission spectrum correspond w the electron jumping from _____ levels to the ______ energy level
higher
second
when an electron jumps to n3, what is the region and energy level?
infrared
low
when an electron jumps to n2, what is the region
visible
when an electron jumps to n1, what is the region and energy
ultraviolet
high
how to calculate the number of electrons each principal quantum number can hold?
2n^2
how many electrons can the principal quantum number 3 and 4 hold?
well yknow n=1 can have 2 and n=2 can have 8 BUT as it turns out
3 = 18
4 = 32
what is the sequence of letters for the subshells! + how many electrons can each have
s p d
2 6 10
s and p orbital shapes
s is just a sphere around the centre
p is a dumbell shape? along the axes so like an hourglass
what is the ground state of an atom
most stable electronic configuration with lowest amount of energy
what is the Aufbau principle
ground state is acheived by filling subshells with lowest energy first
(does not follow pattern above n=2)
exception to subshell increase in energy as follows: s < p < d < f
3d subshell has slightly higher energy level than 4s = 4s filled first
what does it mean when orbitals are ‘degenerate’?
orbitals in the SAME subshell have the same ENERGY (1s=2s=3s=4s)
subshells can be further divided into orbitals, which each can hold ___ electrons
2
so if theyre like ooh 2p subshell how many orbitals?? well it can hold 6 electrons so 3 orbitals
the size of s orbitals increases with _______ shell number
increasing
so like n=3 is gonna be a bigger sphere than n=1
p subshell has ____ orbitals and they are oriented?
3 orbitals
occupy x,y,z axes perpendicular to each other in a dumbell shape
shape change of p orbitals with increasing principal quantum number?
longer and larger lobes
what is spin-pair repulsion?
when 2 electrons spinning in the same direction (same spin) repel each other
what is Hunds rule?
due to spin-pair repulsion, electrons occupy seperate orbitals before pairing up with another with opposite spin
(basically in the square thing, you fill in ^ ^ ^ before going ^v ^v ^v)
what is the Pauli Exclusion principle?
an orbital can hold 2 electrons and they must have opposite spin
how does shorthand electron configuration work
use the nearest preceding noble gas + rest of the config
[Ar]3d^54s^1
transition metals fill the 4s/3d subshell first and lose electrons from the 4s/3d subshell first
4s !!!
according to electronic configuration, how is the periodic table split up?
left grp: s block
mid (transmetals): d block
right (nm): p block
below: f block
name the 2 exceptions to Aufbau principle
Cr (Chromium)
Cu (copper)
Cr is NOT 3d4 4s2 it is?
3d5 4s1
why are Cr and Cu exceptions to Aufbau principle
its more energetically favourable to have a full/half 3D SUBSHELL than a full 4s
when energy is released when electron goes from n=2 to n=1, what series does it correpsond with?
ultraviolet
Lyman series
what is Bohr’s model?
idea that electrons exist in discrete energy levels SO an EXACT amt of energy is needed to ‘jump’ an energy level
3 limitations of Bohr’s model
- assumes positions of electrons are FIXED
- assumes energy levels are SPHERICAL in nature
- only applicable to HYDROGEN
what is the limit of convergence?
the frequency at which the spectral lines appear to meet // converge
= first ionisation energy
frequency of radiation in emission spectrum at the limit of convergence can be used to determine the ?
first ionisation energy
what is the first ionisation energy from the Lyman series?
UV region! limit of convergence = energy given out when electron falls from n=infinite to n=1
what data booklet constant will you need to calculate first ionisation energy using convergence limit?
plancks constant!
in the conversion between wavelength and frequency whats the unit for wavelength
m!
so if its nm then you gotta x10^-9
convert J to kJ
divide by 1000
2 things to rmb when calucating first ionisation energy from convergence limit
convert to per mole using AVOGARDOS CONSTANT
convert final units to kJ/mol (if asked for)
- all eqns in formula booklet
4 factors affecting first ionisation energy
- size of nuclear charge
- distance of outer electrons from nucleus
- shielding effect (inner electrons)
- spin pair repulsion
first ionisation energy ______ across a period and _______ decreases down a group
increases
decreases
(top right corner highest)
explain the increase in ionisation energy across a period 4
nuclear charge incr
atomic radius decr = decr dist
shielding constant
harder to move electron = more energy needed
dips in the trend of first ionisation energy increasing across the period name 2
between beryllium and boron
between nitrogen and oxygen (spin-pair repulsion)
why is there a dip in the ioniastion energy trend between beryllium and boron
distance
5th beryllium electron is in 2s
BUT
5th in boron is in 2p (further) = lower
why is there a dip in the ioniastion energy trend between nitrogen and oxygen
spin-pair repulsion in 2p orbital of oxygen
nitrogen has
p orbital ^ ^ ^
oxygen has
p orbital
^v ^ ^
= repulsion = easier to remove = decr first ionisation energy
how does first ionisation energy change one period to the next + why? (dist, shielding, charge)
it has a LARGE DECREASE
- incr dist
- incr shielding bc new shell
- outweighing the incr nuclear charge
why do successive ionisation energies increase
remove first electron = ion
more difficult to remove electron
attractive forces incr with electron decr
- decr shielding
- incr charge
also depends on electronic configuration
big jumps in successive ionisation energies = ?
change of shell
(so if 2nd is hard to remove, there is 1 valence electrion)
(smaller jumps = change of subshell)
