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Physical
Yr 12
Atomic structure
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Cards (27)
What does the atomic number tell us about an element?
The number of
protons
Define relative atomic mass.
The
average
mass
of an of an element relative to the 1/2 the mass of an atom of
carbon-12
Define an isotope.
Different forms of the same
element
, which has the same number of
protons
but different number of
neutrons.
So they have the same
chemical
properties.
Outline process of electrospray ionisation
The sample is dissolved in a
volatile
solvent
Then is
injected
with a fine
hypodermic
needles to create an
aerosol
The end of the needle is attached to a
high
voltage
power supply
Producing an
xH+
ion
Outline the process of electron impact ionisation
The sample is
vaporised
Then the
electron
gun
knocks of one
electron
from the
molecule
Forming a X+ ion and an
electron
Define the first ionisation energy
The amount of
energy
required to remove one
mole
of
electrons
from one
mole
of
gaseplus
atoms to form one
mole
of
gaseous 1+
ions
Describe how time of flight mass spectrometer works
Ionisation
- electrospray or electron impact
Acceleration
- the ions are accelerated so they all have the same
kinetic
Ion
drift
- all the ions move at the same kinetic energy (
larger
mass =
slower
velocity) (smaller mass = higher velocity)
Detection
How are the ions in mass spectroscopy detected and measured?
Positive ions hit the
negatively
charged plate and pick up an
electron.
The
movement
of electrons causes a
current
which can then be measured.
Time of flight Equation
t
=
t=
t
=
d
(
2
r
o
o
t
)
m
/
2
K
E
d(² root)m/2KE
d
(
2
roo
t
)
m
/2
K
E
How do you calculate Ar
Ar = (
mass
×
abundance
) + (
mass
×
abundance
) /
total abundance
Kinetic energy equation
K
e
=
Ke =
Ke
=
1
/
2
m
v
2
1/2 mv²
1/2
m
v
2
Calculating velocity using Ke
V = (² root)
2Ke
/
m
What is the molecular ion peak?
The
last significant
peak on the graph
On a mass spectrum for electronic impact what are many smaller peaks together showing?
Fragmentation
On a mass spectra for electrospray Ionisation, what are smaller peaks due to?
Isotopes
(e.g. C¹³ or H²)
Equation for the first Ionisation energy if Al
Al(g)
-> Al+(g) + e‐
Equation for the second ionisation of Ca
Ca
+(g) ->
Ca2
+(g) + e‐
Equation for the third Ionisation energy of Fe
Fe2+
(g) ->
Fe3+
(g) + e-
From a series of Ionisation energies of an element, how would you find which group its in?
Look for the
large
jump
in Ionisation energies ( e.g 4 -> 5th means its in group 4)
Name the 3 factors effecting Ionisation energies:
Distance from nucleus
Nuclear charge
Shielding
How does shielding effect the Ionisation energy?
Attraction from the
nucleus
is
shield
by
inner electrons
More
shells = more shielding =
less
energy needed to
remove
electrons
How does nuclear charge effect Ionisation energies?
Greater
nuclear charge = more
protons
(increased
attraction
between nucleus and outer e-)
So more attraction =
more
energy needed to remove
As e- are removed number of
protons
remains the
same
=
greater
nuclear charge
How does distance from nucleus effect Ionisation energy?
Further
away
the
outer
e- from nucleus =
less
attraction between them
So
less
energy need to remove them
Why is there a did in the transect of first ionisation energies of period 3 elements at aluminium?
The
outer
e- is in the
3p sub-shell
, which is slightly further away from nucleus and has
shielding
from
3s
, so takes slightly
less
energy to remove
Why is there a did in the transect of first ionisation energies of period 3 elements at sulfur?
Two
electrons are
paired
in the
3p
orbital
So there's
e- e-
repulsion
means it requires slightly
less
energy to remove it
Why does the first ionisation energy decrease down the group?
Atoms get
bigger
, so electrons removed from
higher
energy level
The other e- is
further
from the nucleus
More
shielding
Less
attraction between e- and nucleus
Less
energy need to remove the e-
Why is there a big jump in ionisation energies?
After all
electrons
have been
removed
from on
sub-shell
it moves to the next
Less shielded
=
stronger attration
= more
energy
needed