Atomic structure Flashcards
where are protons, neutrons and electrons located in an atom ?
protons and neutrons are located in the middle of the atom (nucleus)
electrons occupy energy levels/ shells that orbit the nucleus
what is the atomic number ?
the number of protons (and electrons) in an atom of an element
normally the smaller number
what is the mass number ?
this is the amount of protons and neutrons combined
when can an ion be positive or negative?
positive = protons > electrons
negative = protons < electrons
what is an isotope ?
isotopes are atoms with the same number of protons and a different amount of neutrons
what is evidence to support Rutherford’s model ?
and why is Neil Bohr’s model have shells ?
at point P most alpha particles were detected so he concluded atom is mostly made out of open space
at point Q 1 out of 8000 alpha particles was detected which he concluded particle was repelled by a small-dense, positive nucleus
Neil Bohr’s model having shells comes from measuring ionisation energies
what’s the definition for ionisation energy ?
ionisation energy is the amount of energy needed to remove a mole of electrons from a mole of atoms in the gaseous state
e.g,
C (g) ——> C+ (g) + e-
three factors which effect ionisation energy ?
1) nuclear charge (number of protons)
2) distance from nucleus
3) sheilding
electron shells
s = 2e-
p = 6e-
d = 10e-
f = 14e-
what goes before the d sub shell
4s2 comes before 3d10
1s2 2s2 2p6 3s2 3p6 4s2 3d10
why is it easier to remove an electron in the P subshell compared to the S subshell when there’s only one electron in the P subshell
p subshell is higher in energy which makes it easier to remove an electron
why is it easier to remove an electron from a paired P subshell compared to a P subshell with an unpaired electron
because electrons in a paired subshell repel making it easier for an electron to be removed
which two anomalies are in the 4s2 3d10 subshells
1) chromium
should be - 1s2 2s2 2p6 3s2 3p6 4s2 3d4
is actually - 1s2 2s2 2p6 3s2 3p6 4s1 3d5
thus making it more stable
2)copper
should be - 1s2 2s2 2p6 3s2 3p6 4s2 3d9
is actually - 1s2 2s2 2p6 3s2 3p6 4s1 3d10
thus making it more stable
how does the ionisation energy change down a group ?
atoms get bigger
more shielding
weaker attraction from nucleus to electron in outer shell
ionisation energy decreases down the group
trends going across group 2 and 3
generally increases in ionisation energy going across the groups
as you go across - the nuclear charge increase
they have the same shielding
so a greater attraction between the nucleus and the outer electron
why are sample particles ionised ?
so they can accelerate towards the negatively charged plate
so they can generate a current when they hit the detector
how is the ion accelerated ?
positive ion attracted to negative plate
all ions have the same kinetic energy
how are ions separated in the flight tube ?
ions travelling at higher speeds have a smaller mass
ions travelling at slower speeds have a higher mass
how are ions detected ?
each ion hits the detector
ion gains an electron
generates a current
size of the current is proportional to the abundance of the ion
electrospray ionisation
1) the sample is dissolved in a volatile solvent
2) The solvent is injected using a hypodermic needle producing a fine mist
3) The needle is attached to a high voltage power supply, so as the sample is injected
4) the particles are ionised by gaining a proton from the solvent
X (g) + H+ → XH+ (g)
5) The solvent evaporates and the XH+ ions are attracted towards a negatively charged plate
This accelerates them through the mass spectrometer
1) sample dissolved in volatile solvent
2) injected through a fine hypodermic needle giving a fine mist
3) tip of needle has high voltage
4) each gains a proton as it leaves the needle
electron impact
1) The sample being analysed is vaporised and then high energy electrons are fired at it.
2) The high energy electrons come from an ‘electron gun’ which is a hot wire filament with a current running through it that emits electrons.
3) This usually knocks off one electron from each
particle forming a 1+ ion.
X(g) ——> X+(g) + e-
4) The 1+ ions are then attracted towards a negative electric plate where they are accelerated.
1) high energy electrons
2) from electron gun
3) fired at sample
4) knocks of one electron
learn Ar - abundance - KE
from the booklet and questions
how TOF works
vacuum
ionisation
acceleration
ion drift
detection
data analysis
what happens to the 4s2 sub shell first and then the 3d10 subshell ?
the 4s2 subshell gains and looses electrons first and then the 3d10 subshell does
