atomic structure Flashcards
atomic number
amount of protons
what expression gives mass number
proton number plus neutron number
expression for proton number
mass number- neutron number
expression for neutron number
mass number - proton number
whats mass number
neutron number plus proton number
atomic mass unit
measures weight of atoms 1/12 of carbon 12
how to calculate relative mass
take isotope and times relative abundance by atomic mass
add together and divide by 100
symbol for relative atomic mass
Ar
whats the relative atomic mass definition
the average mass of one atom of an element relative to one twelfth of the mass of carbon 12
kinetic energy equation
0.5 times mass times velocity squared
unit for kinetic energy
Joules
unit for mass in kinetic energy
kg
rearranged kinetic energy equation for mass
m= 2ke/v squared
rearranged equation of kinetic energy for speed
v= square root 2ke/m
time of flight
distance travelled by atom to calculate its mass
equation for atoms mass from time of flight
m=2ke times t squared/distance aquared
rearranging time of flight formula for time subject
t= root distance root m/2ke
time of flight mass equation for distance subject
d= root t times root 2ke/m
why do we turn atoms into ions in time of flight
because atoms nuetral they need charge to be attracted to charged metal plate
what do we need to do so charged plate can give atoms kinetic energy
ionise them
whats a time of flight mass spectrometer
measures time of flight of atom to work our mass of atom
4 steps of mass spectrometry
-ionisation
-acceleration
-ion drift
-detection
electron gun ionisation
hot wire that emits electric current which emits fast moving electrons and knocks electron of atom and makes positive charged atom
vaporisation
to get atoms ready for electron gun they are heated to get ready for electron gun
accelaration step
negative charged plate moves positive atom towards it
-atom gains kinetic energy and speed
what determines how much energy ion receives
the charge of the atom so big or small all ions have the same kinetic energy as all equal in charge
ion drift stage
- hole in negative plate allows ion to move distance down tube
-distance known
-flight tube
-
drifting ion
when ion moves through flight tube with known charge and kinetic energy and mass
how to get ion to drift
suck all air out of flight tube to allow ion to drift
detection stage
when electrons hit negative final plate electric current given off measured by computer
-bigger the current the large the movement
gain an electron
how to determine mass of atom in spectrometry
measure time taken to reach detector
how to determine number of atoms of particular mass in spectrometry
size of electrical current at detector
what happens after detection
computer produces mass spectrum
x and y axis of mass spectra
mass/charge ratio and relative abundance
how to calculate RAM from mass spectra
identify ions -mass number
-express relative intensity in percentage
-total ions divide by how many of ions your working out times 100 as percentage
-percentage of each times mass number adding individuals up dividing all by 100
formula for comparing two ions to predict flight of mass
m1/t2 = m2/t2
rearranged equation for comparing two ions flight of mass
t2 = root m2/m1 times t1
bohr model of the atom
orbits electron in 3D
at specific distances from nucleus
how are electrons quantised
because of fixed distance from nucleus they are restricted to energy levels
how to go up energy level or down
lose or gain energy
1 way of electron gaining energy
absorbing light
why do electrons only absorb specific colours
energy quantised so cant have any energy it likes
-not all colours absorbed
good things with bohr rutherford model of atom
- no evidence electrons spiral into nucleus
-uses data to made predictions
-elegant and clear
-good at explaining chemistry
schrodingers model of atom
-electrons energy quantised
-energy levels would be exactly values earlier experiment shown
how to find electrons energy levels
free electron and find out gaps between jumping from energy level to level
-relative to free electron
orbital
space where electrons can be
probability
-where electrons can be most of the time
orbitals in first energy level
1
orbitals for second energy level
4
orbitals for third energy level
9
orbitals for fourth energy level
16
s sub level orbitals
1
p sub level orbitals
3
d sub level orbitals
five orbitals
f sublevel orbitals
7 orbitals
naming sub levels
1s
2s
3s
4s
1p
2p
3p
4p
and so fucking on
difference between 2s and 3s sub level
-energy of sub level
-radius of the orbital in the sub level
ground state
lowest energy level of atom
energy levels with more protons
stronger gaps between levels so stronger attraction
energy of atoms when adding more electrons
more gaps and energy levels break down into sub levels
repulsion of electrons
order of sub levels
s
p
d
f
lowest to highest energy levels order
1s
2s
2p
3s
3p
4s
3d
4p
5s
4d
5p
6s
aufbau principle
build up on electron configuration from lowest energy sub levels
pauli exclusion principle
an orbital can contain a max of two electrons
max electrons for s sub level
2
mas electrons for p sub level
6
max electrons for d sublevel
10
d block of table
group 1 and 2 and hydrogen
p block
group 3 4 5 6 7 0
d block
all transition elements
shorthand electron configurration
element before with added configuration with elements own notation
spin
spin up and spin down
problem with spin
not electrons spinning but quantam effect
rules of spin
pauli says cant have sub level with 2 or more electrons with same spin
pauli exclusion principle
no orbital cant have same spin electron
hunds rule
-within a sub level every orbital is singly occupied before any doubly occupied
-all electrons in singly occupied orbitals have the same spin
why do orbitals in the same level have single spin before they become doubled
-electrons in same orbital repel each other more than electrons in different orbitals
-electrons occupy different orbitals to reduce repulsion
find out electron conc of ions
electron conc of cations
remove electrons with highest energy from origional conc
electron config of anions
add electrons to original config
nuclear charge
how many protons are in nucleus
how does nucleus charge effect electrons
larger charge is more
= more protons so more force electrons have on them
as you across period how does nuclear charge change
increases by 1
nuclear charge change as going down group
increases by more than 1
distance from nucleus
-further away less electrostatic force
-weaker force of attraction
-lower energy levels have electrons closer to nucleus
protons and distance
higher nuclaeu charge closer each shell is to nucleus
what effects the distance between nucleus and outer electrons
nuclear charge and which shell the outer electrons are in
distance down group
increases as electrons in different shell so further away fromn nucleus
electron electron repulsion effect on electrostatic force on electron
because electrons repel each other that decreases some of force felt by electrons because of protons
rules of shielding
-electron closer to nucleus shields charge of one proton
-electron in same shell shields small amount of one proton
-electron further in shell doesnt shield at all
moving across period for shielding
number of outer electrons increases so shielding increases
down group shielding
increases because new shell made
factors that effect forces on electrons
-nuclear charge
-distance from nucleus
-shielding
group 1 elements and water
-electrons removed
-higher energy level equals less energy to move
-moves from highest energy sublevel
first ionisation energy
the energy required to remove one mole of electrons from one mole of gaseous atoms of element
unit for ionisation energy
KJ/ mole
first ionisation energy equation
element(g) + element ion (g) + e-
first ionisation energy down a group
decrease down group
-attraction to nucleus decreases
first ionisation energy across period
–increases
-nuclear charge increases
-harder to remove electrons
-generally increases
why do ionisation energies decrease down group
-weaker attraction to nucleus
-outer electrons more shielded and further away from nucleus
-
why first ionisation energy across period generally increases
-nuclear charge increases
-shielding of outer electrons stays roughly the same
-strong attraction to nucleus
why does potassium have lower ionisation energy than sodium
potassiums outer electron more shielded and further away from nucleus
weaker attraction to nucleus
why does magnesium have higher ionisation energy than sodium
-magneisum gas higher nuclear charge than sodium and both atoms have same shielding since in same shell
-masgnesiums outer shell electrons have stronger force of attraction to nucleus than sodium
magnesium and aluminium first ionisation energies
-Al has lower first ionisation energy than magnesium
-Al electron removed from 3p but Mg from 3s
-3p sublevel further away from nucleus and also shielded by aluminiums 3s electrons
-less energy to remove electron from AL
-
phosphorus and sulfur ionisation energies
-sulfur has paired electron in 3p sublevel
-electron repulsion between pairs
-less energy needed
second and so forth ionisation energy
removing second and whatnot electrons from ions
successive ionisation energies
-always increasing
-in certian points bigger jumps
second ionisation energy deifnition
the energy required of an element to remove one mole of electrons from one mole of gaseous 2+ ions of that element
why do successive ionisation energies always increase
because electrons are removed from a increasingly positive ion which requires more energy
how do graphs of successive ionisation energies give evidence for shells
-big jumps give evidence for shells
-we can explain jumps by saying electron is being removed from an inner shell
how does graph of first ionisation energy across period give evidence for subshells
-drop between al and mg on graph give us evidence
-Al has greater nuclear charge than mg so first ionisation would be greater
Al lower than mg so Al outer electorn in different sublevel
how does graph of first ionisation energy across period give evidence that electrons in same orbital repel more than electrons in different orbital
-drop between P and S
-sulfur has greater nuclear charge than P
-sulfur isnt higher than P so idea that electrons in same orbital repel each toher more
rutherford and current model difference
-current model has neutrons and protons but rutherfords doesnt
-current model shows electrons in different energy levels- rutherfords doesnt
missing percentage abundance
add al known percentages and take away from one hundred
equation for electrospray ionisation
X(g) + H+ → XH+(g)
define mass number of an atom
number of protons and neutrons in nucleus of atom
finding number of neutrons
take away top number from proton number
number of protons same as
number of electrons
define relative atomic mass
average mass of an atom of an element compared to 1/12 the mass of carbon 12 atom
working out RAM when given relative intensities
add all intensities up and divide by total number
why you need to ionise atoms before doing time of flight
-ions will interact with and be accelerated by electrical current
-ions create current when hitting detector
describe how molecules are ionised using electrospray
-sample dissolved in volatile substance
-injected through needle at high positive charge
-each molecule gains a proton
explain first ionisation energies pattern from lithium to neon
general trend li to ne
-first ie increases
-more protons
-electrons in same shell
-no extra shielding
-stronger attraction between nucleus and outer electrons
deviation be - B
-B lower than Be
-outer electron in 2p
-higher in energy than 2s
deciation N to O
-O lower than N
-2 electrons needed in 2p to pair
-pairing electrons cause repulsion
role of water with calcium reaction
oxidising agent
trend in group 2 first ionisation energies
-decrease
-ions get bigger
-weaker attraction of ion to lost electron
electron impact ionisation
sample bombarded with high energy electrons
-sample of molecules lose electron forming positive ion
how TOF separates two species to give peaks
-positive ions accelerated by electric field
-to constant kinetic energy
-all have same kinetic energy
-so lower mass ratio move faster
how to predict m/z ratios on graph
add all possibilities of all isotopes added up
2 combinations
how to work out relative intensity of peaks
work out probability of each isotope in each combination and put into fraction and times fractions
small peaks on mass spectra
caused by fragmenting of molecules with electron gun
