Atomic Structure Flashcards
why do isotopes of the same element have the same chemical properties
they have the same electron configuration
state the different atomic models in chronological order
john dalton- solid sphere model
j.j thomson- plum pudding model
ernest rutherford- nuclear model
niels bohr-planetary model (current)
erwin - quantum model
summarise the properties of the subatomic particles
proton neutron electron
relative mass 1 1 1/1840
relative charge +1 0 -1
what does the charge of an atom show
numbers of electrons gained/lost
why do isotopes have different physical properties
they have different numbers of neutrons so they have different masses
describe what evidence was found to support Rutherford’s model
-rutherford fired He^2+ ions (alpha particles) at a sheet of gold foil, most went through to other side but small amount bounced back
-when these ions were detected behind the gold foil he concluded that most of the atom was empty space
-when a small number of ions were detected in front of the gold foil he concluded that the atom had a small positive nucleus
what are the key differences between Thomson’s and Bohr’s model
-the bohr model has a positive nucleus
-the bohr model has protons and neutrons in the nucleus
-bohr’s model has electrons in shells/energy levels and these orbit the nucleus
where did the evidence to support the electrons being arranged in shells come from
from measuring ionisation energies
define ionisation energy
IE is the amount of energy needed to remove one mole of electrons from one mole of atoms in a gaseous state
write an equation for the first ionisation energy of potassium
K (g)→K+ (g) + e-
what 3 factors will influence ionisation energy
nuclear charge (num of protons)
distance from nucleus
shielding
what are the series of ionisation energies known as
SUCCESSIVE ionisation energies
what happens to the IE when an electron is removed from a new shell
there’s a large increase in IE as the electron being removed is closer to the nucleus
which element has the highest 1st IE
Helium because it has the least amount of shells and shielding than any other atom so it will have the strongest attraction between its outer electron and nucleus so lots of energy s needed to remove its electron.
why is Li a bigger atom than Be
-they are on the same period so they have similar shielding however
*Be has more protons than Li so it has a stronger attraction between the outer electron and nucleus therefore
-t goes closer to nucleus.
why is Li a bigger atom than He
-it has more shells than He so there’s more shielding
-so there’s a weaker attraction between outer electron and nucleus as there’s a larger atomic radius
-so He will go closer to nucleus
why is Li+ a smaller ion than F-
-F- has more shells than Li+ so it has a greater distance and more shielding
-so there’s a weaker attraction between its outer electron and nucleus
-so its bigger
where are orbitals found
within each shell there’s a sub shell and within each subshell we find orbitals
what is an orbital
its a region within an atom which can hold up to two electrons with opposite spins
how many orbitals is there in;
-the s sub-shell
-the p sub-shell
-the d sub-shell
- 1
-3
-5
what is the maximum number of electrons in each shell;
-1
-2
-3
-4
-2
-8
-18
-32
what is the shape of an s orbital
circle
what is the shape of the p orbital
like an eight/infinity sign
which orbitals are the lowest energy ones
the ones closer to the nucleus
which electron is determined the highest energy
the outer most electron because its furthest from nucleus
give the electron configuration of potassium
1s2 2s2 2p6 3s2 3p6 4s1
give the electron configuration for chromium
1s2 2s2 2p 3s2 3p6 4s1 3d5
give the electron configuration for copper
1s2 2s2 2p6 3s2 3p6 4s1 3d10
give electron configuration for a CU2+ ion
1s2 2s2 2p6 3s3 3p6 3d9
why does B have a dip in 1st IE
-in Be the outer electron is on 2s2 and on B its on 2p1
-2p is higher energy than 2s
-therefore there’s going to be a weaker attraction between the outer electron and nucleus
why does O have a dip in 1st IE
-there are a pair of electrons in O on 2p orbital
-the electrons will repel so less energy is needed to remove electron
how does IE change down a group
IE decreases because as you go down a group the atom size increases and there are more shells so there’s more shielding. therefore the distance between the nucleus and outer electron increases and the attraction weakens, so less IE is needed.
what does a mass spectrometer measure
-relative abundance
-mass/charge ratio (m/z)
what are the steps for mass spectrometer
-insert sample in vacuum chamber and ionise
-acceleration
-ion drift
-ion detector
-data analysis
why is the entire mass spectrometer in a vacuum
to prevent any particles being tested colliding with molecules from the air
what are the methods of ionisation
-electron impact and electrospray ionisation
describe the acceleration stage in flight tube
-positive ions are attracted to a negatively charged plate and accelerate towards it at constant KE
-the acceleration depends on their mass to charge ratio
describe the ion drift
-ions will form a beam of particles ad travel along flight tube, towards detector
-ions have different velocities and they are separated due to their mass
-heavier ions travel slower
-lighter ions travel faster
-therefore they are all detected at different times
describe detection
-different m/z ions arrive at detector/negatively charged plate
-once an ion hits the detector, it gains an electron and this floe of electron generates a current which is proportional to the abundance
describe data analysis
signal from detector is passed to a computer which generates a mass spectrum
why are sample particles ionised
-so they can be accelerated towards the negatively charged plate
-to generate a current when hitting the detector
how is the ion accelerated
-positive ions are attracted to the negatively charged plate to a constant KE
what does each peak on a mass spectrometer graph represent
a different isotope
escribe electron impact ionisation
-sample is vaporised
-high energy electrons are fired from an electron gun
-which is a hot wire filament with a current that emits electrons
-high energy electrons knock off one electron from sample forming a positive ion
which ionisation technique is used for elements and substances with low formula mass
-electron impact
-and causes the (molecular) ion to break down into fragments
give general equation for electron impact ionisation
X (g) → X+ (g) + e-
describe electrospray ionisation
(this process is for substances with higher molecular mass like proteins)
-sample is dissolved in volatile solvent
-and injected through a fine hypodermic needle to give a fine mist (aerosol)
-top of needle has a high voltage power supply
-and particles are ionised by gaining a proton (H+)
give the general equation for electrospray ionisation
X( g) + H+ → XH+ (g)
calculate the peaks of Br2
79-81
50% each
79-79=1/4
79-81 and 81-79 = 2/4
81-81= 1/4
25%=158
25%=162
50%=160
what is the structure to find highest IE when both one atom’s electrons are on p3 and the other on p4
- there is a pair of electrons on _p orbital
- these electrons will repel
- so less energy is needed to remove electron
what is the structure to find higher IE when each atom’s outer electron is on a different sub-level on same shell
- state location of outer electron
- _p is higher energy than _s
-compare attraction between outer electron and nucleus
