AQA A-Level Chemistry - Ionisation Energies
Summary
TLDRThis educational video script delves into the concept of ionization energy, a crucial topic in chemistry often featured in exams. It defines ionization energy as the energy required to remove an electron from each atom in a mole of gaseous atoms to form ions. The script explains the factors influencing ionization energy, including nuclear charge, electron distance from the nucleus, and shielding effects. It also discusses trends in ionization energy across the periodic table, highlighting how these energies increase across a period and decrease down a group. Practical examples using elements like oxygen, magnesium, and sodium are provided to illustrate the principles, and the script concludes with strategies for identifying elements from their ionization energy patterns.
Takeaways
- 🔬 Ionization energy is the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous ions.
- 📚 Memorizing definitions is crucial for scoring well on exams, as they are straightforward to understand and remember.
- 📈 The first ionization energy is the energy needed to remove an electron from a neutral atom, while subsequent ionization energies involve removing electrons from increasingly positive ions.
- 🔋 The number of the ionization energy asked for corresponds to the charge of the ion produced; for example, the fourth ionization energy results in a 4+ ion.
- ⚛️ Three main factors affect ionization energy: the charge of the nucleus, the distance of the electron from the nucleus, and electron shielding.
- 📉 As you move down a group in the periodic table, ionization energy generally decreases due to increasing atomic size and distance from the nucleus.
- 📈 Conversely, across a period, ionization energy increases due to decreasing atomic size and increasing nuclear charge, despite constant electron shielding.
- 📊 Graphs of ionization energy can be used to identify elements by their distinctive patterns of increases and jumps, which correspond to electron shell transitions.
- 🔑 Understanding the trends in ionization energy can help in predicting the values for consecutive ionization energies and even identifying elements from given data.
- 💡 The video provides practical exam strategies, such as using the differences in ionization energy values to estimate unknown values, which is a valuable skill for exams.
Q & A
What is ionization energy?
-Ionization energy is the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous ions.
Why is it important to know the definition of ionization energy for exams?
-Knowing the definition of ionization energy is crucial for exams because it can be a straightforward way to earn marks, and memorizing definitions can be the difference between different grade boundaries.
What is the first ionization energy of oxygen, and how is it represented?
-The first ionization energy of oxygen involves the removal of an electron from a mole of oxygen atoms (O) to form a mole of oxygen ions (O^+) and a mole of electrons.
How does the charge of the nucleus affect ionization energy?
-The charge of the nucleus increases the attractive force between the nucleus and the outer electrons, making it more difficult to remove an electron and thus increasing the ionization energy.
What is the relationship between the distance of an electron from the nucleus and ionization energy?
-Electrons that are further from the nucleus experience less attraction and are easier to remove, resulting in a lower ionization energy compared to electrons closer to the nucleus.
How does electron shielding influence ionization energy?
-Increased shielding by inner electron shells reduces the effective nuclear charge felt by outer electrons, making them easier to remove and thus decreasing the ionization energy.
What is the significance of consecutive ionization energies in identifying elements?
-Consecutive ionization energies can be used to identify elements by recognizing patterns in the energy required to remove electrons from different energy levels.
How does the trend of ionization energy change as you move down a group in the periodic table?
-As you move down a group in the periodic table, the ionization energy generally decreases due to an increase in atomic size, distance from the nucleus, and shielding, despite an increase in nuclear charge.
What is the pattern observed in the consecutive ionization energies when moving from one energy level to another?
-There is a steady increase in ionization energy as electrons are removed from the same energy level, followed by a significant jump when moving to a lower energy level closer to the nucleus.
How can you estimate the third ionization energy of magnesium using the given data?
-By observing the trend in the consecutive ionization energies and using the difference between the first and second ionization energies, you can estimate the third ionization energy by extrapolating this trend.
Why is it easier to remove an electron from potassium compared to sodium?
-It is easier to remove an electron from potassium compared to sodium because potassium is lower in the same group of the periodic table, has a larger atomic size, and thus a lower ionization energy due to increased distance and shielding effects.
Outlines
🔬 Understanding Ionization Energy
The paragraph introduces the concept of ionization energy, emphasizing its importance in chemistry exams. It defines ionization energy as the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous ions. The paragraph stresses the need to memorize this definition for exams and explains the process using oxygen and magnesium as examples. It also discusses the first ionization energy and how it differs from higher ionization energies, noting that each subsequent ionization requires more energy due to the increased positive charge of the ion from which the electron is being removed.
📚 Factors Influencing Ionization Energy
This section delves into the factors that affect ionization energy: the charge of the nucleus, the distance of the electron from the nucleus, and electron shielding. It uses a sodium atom as an example to illustrate how these factors influence the ease with which an electron can be removed. The paragraph explains that a higher nuclear charge results in a stronger attractive force and thus a higher ionization energy. Conversely, greater distance and increased shielding decrease ionization energy. The discussion also touches on how these factors change as electrons are removed successively, leading to higher ionization energies for removing electrons from increasingly positively charged ions.
📉 Trends in Ionization Energy
The paragraph discusses the trends in ionization energy within the periodic table, focusing on the differences between moving down a group and across a period. It explains that ionization energy generally decreases down a group due to increasing atomic size and distance from the nucleus, which outweighs the increase in nuclear charge. In contrast, ionization energy increases across a period as the atomic size decreases, the nuclear charge increases, and shielding remains constant. The paragraph also includes a graphical representation to illustrate these trends and discusses how the consecutive ionization energies of elements can be used to identify elements based on their electron configuration.
🔍 Identifying Elements Through Ionization Energy Trends
This section explores how to use the trends in ionization energy to identify elements. It provides a method for determining the number of electrons in an element's outer shell by analyzing the jumps in ionization energy values. The paragraph uses carbon as an example, showing how its ionization energy values correspond to its electron configuration. It also discusses how to estimate the third ionization energy of magnesium by using the differences in known ionization energies and the trend of increasing values. The paragraph concludes with a practical example of estimating ionization energy values and emphasizes the importance of understanding electron arrangements for such calculations.
🗣️ Closing Remarks on Ionization Energy
The final paragraph wraps up the discussion on ionization energy, summarizing the key points covered in the video. It encourages viewers to be prepared for questions related to ionization energy in exams and invites them to leave comments, requests, or questions for further discussion. The paragraph reiterates the importance of understanding the concept of ionization energy and the factors that influence it, as well as the ability to apply this knowledge to identify elements and solve related problems.
Mindmap
Keywords
💡Ionization Energy
💡First Ionization Energy
💡Second Ionization Energy
💡Charge of the Nucleus
💡Distance from the Nucleus
💡Shielding
💡Consecutive Ionization Energies
💡Periodic Trends
💡Electron Configuration
💡Gaseous Ions
💡State Symbols
Highlights
Ionization energy is the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous ions.
Understanding ionization energy is crucial for answering questions on exams, as it can be straightforward to score marks on.
The definition of ionization energy includes the state symbol 'G' for gaseous, which is essential for scoring marks.
First ionization energy involves removing an electron from a neutral atom, while subsequent ionization energies involve removing electrons from increasingly positively charged ions.
The number of the ionization energy requested corresponds to the charge of the ion produced.
Three main factors affect ionization energy: the charge of the nucleus, the distance from the nucleus, and shielding by inner electrons.
A stronger nuclear charge results in a greater ionization energy due to a stronger attractive force on the electrons.
An electron that is further from the nucleus requires less energy to remove, compared to one closer to the nucleus.
Increased shielding by inner electron shells leads to a decrease in ionization energy as it reduces the effective nuclear charge felt by outer electrons.
As you move down a group in the periodic table, ionization energy generally decreases due to increasing atomic size and distance from the nucleus.
Across a period, ionization energy increases due to decreasing atomic size and increasing nuclear charge, despite constant shielding.
Consecutive ionization energies increase as you remove electrons from a given energy level, with a significant jump when moving to a lower energy level.
The pattern of ionization energy changes can be used to identify elements based on their electron configuration.
Exam questions may ask to predict ionization energies of elements based on their position in the periodic table and known trends.
The video provides a method for estimating ionization energies by using the differences between known values and trends.
Understanding the trends in ionization energies can help in predicting the values for elements not directly given in the data.
The video concludes with a summary of key points about ionization energy, emphasizing the importance of definitions and trend analysis for exam success.
Transcripts
right so this video is going to cover
ionization energies um it's a
fairly uh it's a reasonably small topic
but it's one that um almost always comes
up on papers um and it can often have a
question just solar and ionization
energies which is quite a good one to
get marks on because actually it's quite
straightforward so first thing
ionization energy what does that mean
well there's a definition for this and
it's definition that you must learn and
it is as follows it is the
energy required
to
remove one
electron
from each
atom in one
mole of
Gus
atoms to
form one
mole of gasius
ions so that's your definition
now there's obviously within the whole
of the unit one and unit two there are a
few definitions to learn um and you've
got to make sure that you can do them
you can absolutely nail them this might
be worth a couple of marks and actually
if you can just sort of regurgitate that
onto a page that's two easy marks up of
70 for your unit one and that you know
that could be the difference between you
know your C and your b or your B and
your a so it's important to have your
definitions down because there's no
excuse for not getting those those marks
application questions yeah stating stuff
recalling things there's no excuse um so
what does this actually mean well as it
says it's the energy required to remove
an electron from each atom in one mole
of gasius atoms to form one mole of gas
ion so in reality U it would look
something like this so if I take a mole
of oxygen atoms no atoms I'm not doing
O2 here okay we are not dealing with O2
it's purely atoms okay so regardless
whether they're diatomic or what they
are we're just dealing with single atoms
key thing make sure you include the
state symbols because the definition
does State gaseous therefore you must
have that there you haven't got the G
you're not going to get the Mark um
unfortunately so going across we're
going to produce then one mole of gases
again the G
ions and an electron there so one mole
of atoms gives us one mole of ions and
one mole of electrons as well now we
don't have to worry about the numbers of
electrons really we can we can ignore
that you can include that in in the
definition there are a few different
variations of this um but ultimately you
know it could be the energy required to
move a mole of electrons from mole of
gas's atoms Etc there are a few
variations I like this one it makes
sense to me um so this is oxygen just to
give you another one uh magnesium for
example then would be mg gas goes to mg
plus
gas plus electrons now these are both
classed as the
first ionization energy going bate that
to IE so these are the first ionization
energy and what that means it is the um
the the energy value associated with
this would be to remove one electron
from there so our second anization
energy if we were asked to write a
um write an equation to show that it
would be as follows it would be an o
plus this time G going to O
2+ G+ electron on the other hand the
Magnesium would be
mg+ going to
mg2+ plus electron so still the same
thing we got there we've got the Gus
Parts uh and we've got the correct
charges and electrons note though that
we do not start with atoms here for our
second we start with ions and that's
because this is the
second ionization and therefore the
definition changes it's not going to be
the same as the first one this would be
the energy required to remove one
electron from each ion uh each uni
positive or singly positive ion in one
mole of gaseous ions or gaseous uni
positive ions to form one mle of gasius
2 plus ions so you've got to include the
charge into them this is the second
ionization energy now you could be asked
for the fourth ionization energy for
example and I've come up with a
fantastic way of remembering this
and that is that the number of the
ionization energy they ask for that will
equate to the charge of the ion produced
so my fourth ionization energy for
example fourth ionization energy of
chlorine I'm going to be producing the
CL 4 plus ion sticking my gases stick in
my
electron and therefore must start with
the 3+ okay so if you ever get confused
that don't have to worry about counting
up this number here second or fourth or
thir is going to equate to the charge of
the ion produced that's the key thing
charge of the ion produced just bear
that in mind it's it's one that they
could ask you varieties of
these okay so that
is that's how you would write out that
and that comes up very often they love
to ask that because it's a very easy one
to get sort of a mark out of um probably
not going to get two marks or you might
do one for charge one for gous parts oh
error there
um okay so the next thing they like to
do they like to talk about various
Trends and factors that change your
ionization energy there are really three
factors that will
affect
um the ionization
energy and they are as follows we have
the
charge of the
nucleus we have the
distance from the
nucleus and finally you may guess it
we're going to have
shielding so these three things affect
the ionization ionization energy and
they do so because of the following and
I'm going to what I'll do is I'll show
you a sodium atom um in an old school
electron configuration so this is a
sodium atom this is my sodium atom right
here if we look at this as an individual
example
this
electron right up here this would be the
one that's removed as my first
ionization
energy so that's going to be the first
ionization energy then any of these is
going to be our second followed by third
fourth fifth 6th 7th eth 9th then going
down here 10th and 11th so first is
always going to be that one of those
outer shell so we start with the outer
and we work in so the opposite of sort
of how we fill we do the opposite
working backwards and you could do that
you could look at that from the other
point of view of the more the a level
way of writing this out so for a sodium
atom 1 S2 2 S2 2
P6 3 S1 we're removing the 3s then we're
moving the 2p then the 2s and then the
1s so we're going in that order
completely
backwards what you can see here is for
any atom when it says charge the nucleus
the charge at the nucleus dictates of
the attractive force between these outer
electrons
um and and the nucleus so the stronger
the charge of the nucleus the stronger
this force will be therefore the more
tightly this is held the more difficult
it is to remove it therefore the
ionization energy would be greater so
increase
charge um increase ionization energy and
that hopefully makes sense it's held
more tightly therefore we've got to put
more energy in to actually rip it away
distance from nucleus it's a similar
idea if we look at this one here
compared to this one here this electron
if we were to have removed all these
already this one is being removed from a
or it's being removed from from much
closer to the nucleus therefore there's
much more attraction there this one's
much further away there's less
attractions this one would require much
more energy compared to this one so
again um this time we could say increase
distance decrease ionization energy and
finally the shielding one well it's
similar to this distance one really um
because distance and shielding go hand
in hand so this one although it's
further away also has some shielding
from this shell this one has sh further
away but also has shielding there so
same as the distance increase in
shielding increase sorry leads to a
decrease in ionization
energy one other point worth um sort of
talking about here is that factors
affecting ionization energy every time
you remove an electron you create a
positive ion now when you have to remove
that next electron you're removing it
from a positive ion or a more positive
ion which means that it's going to
require more energy so charge a nucleus
you could also sort of
say
um charge
of ion really um and we'll go charge of
atom SL ion so charge of an atom is zero
therefore to remove this would be a
value as once we've removed that we're
going to have a positive ion then when
we remove the second electron we're
removing it from a positive ion
therefore this electron is more strongly
attracted it's it's stuck here more
tightly so we've got to put more energy
into to remove it and so on as we remove
all of the consecutive electrons there
um so there are factors involving the
ionization energy what they like to do
is they might give you two examples they
might give you um sodium and potassium
and ask give you their values of
ionization energies first ionization
energies and ask why the values are
different at which point you would talk
about um in that case charge the nucleus
isn't going to have as much of an effect
that's mostly when we're talking across
the
period these two are going to be down
the
group so for example sodium and
potassium sodium being
here potassium being below it lithium
above above sodium so we're looking at
these two sodium is going to be a
smaller
um
atom therefore because it's smaller this
is opposite so we got less distance
therefore great ionization eny this
one's going to be bigger therefore it's
going to be easier to remove that so
down the group ionization energy is
going to
decrease um as opposed
to Across the period it's going to
increase and the main reason that is
down the group atom size is increasing
distance from nucleus blah blah blah
blah blah across the period the actual
distance is getting smaller and that's
also paired with the fact that the
nuclear nuclear charge is getting
greater and the shielding is remaining
equal um so that's a point to be aware
of and actually the the trend in the
period particularly period 3 um is
covered in another video the periodicity
video um so I'm not going to talk too
much about that there but I will
actually show you now a graph of what it
looks like down the group just to give
you an idea actually how that does
change so I'll just stick that um here
so what we can see here is obviously
this is
Down group one lithium is going to be
our
smallest atom and for this this is going
to be our biggest down here at potassium
and the trend is actually true the
enthalpy change this is the um this is
actual ionization energy in
kog uh per mole that has decreased as I
said it would and the reason there is
because you can see that that we've got
an increase in
shielding we've got increase in
distance and although there is also an
increase in nuclear charge it's
basically it's counteracted by these two
um changes there you go
distance uh increasing and we can see
therefore as obviously with the
shielding as well the um ionization
energy is
decreasing now a couple points here um
this point I want to I want to look at
um what happens really with sort of also
the consecutive ionization energies of
elements so look at sodium first of all
so here we have a graph of uh sodium's
ionization energy so you can see the
ionization energy number going from 1
through to 11 and this is corresponding
to our sodium being 1 S2 2 S2 2 P6 3 S1
so our 11 electrons there and what we're
doing is we're moving this in backwards
so this is our
3s1 this is going to be
2p6
2p5
P4 P3
P2
P1 um S2
S1 and we keep these numbers
in and
finally 1 S2 and 1 S1
so what you can see is is a definitive
change and I've I've used the
logarithmic scale to try and make this
um a little bit more clear it does help
with this slightly otherwise it you
don't see this distance this difference
sorry very clearly particularly because
of the massive change up here what we
see is this very clearly there's this
change and the change is that this first
one's down here relatively low um so
around
700ish when we remove that we have a big
jump up to here up to this point here
and then we go Fairly steadily
increasing as I said before we got a
we're moving from a more positive I on
each time blah blah blah blah blah blah
getting greater and greater and then we
have another jump up here now the reason
for that is that we're actually changing
energy level and that's the distance
coming in here so we're going from
furthest
away to closest up here and that makes
that much difference and you can see
this clear jump
here um and we can see that again if we
were to look at uh magnesium so the same
is true here we can see that we have
again I'm not going to worry putting the
actual electrons in um but what we've
got is we've got third energy shell
here second here and first here so we've
got closest to the nucleus this is
closest to the nucleus and furthest away
from the nucleus and we can see that
same pattern every time our consecutive
one is always increasing but it
increases then big jump increases
increases increases increases big jump
every time we move into the next energy
level the next energy level down down we
have a big jump and what's quite good is
this actually means that we can we can
use this idea to actually identify
elements to an extent so if we were told
what period an element is and we were
given a graph like this uh we could
actually decide what the element was or
if we were given the numbers in the
table we could see what the element was
um so it might look something like this
so here we have we've been given a graph
here or we could have been given these
as values but it doesn't matter but what
we've got is we've got four values
increasing big jump big big job we can
see we're going from about 6,000 is
around here so
6,000 around about 6,000 up to what
37 and a half thousand something like
that so we've got a massive jump up
between there massive massive jump which
to me instantly tells me that well that
means I must be moving into a different
energy level so if I'm removing four and
then I'm jumping there must be four
electrons in this outer shell so I'm
looking for an element with four
electrons in the outer shell now I would
be told in the question that this is a
period 2
element um and I'm asked then to you
know what's the identity of the element
so I'm in period two I've got four
electrons in the out shell and just to
sort of reiterate how I got that point
so I'm removing one 2 3 4 not much of an
increase there is an increase but it's
not it's it's it's a steady increase as
I'd expect this jump tells me I'm moving
to a different energy level now because
these are all six of them we've got six
electrons here we've got a big jump
between this fourth uh fourth electron
and the fifth electron being removed
there which tells I'm moving from an
outer shell into an inner shell means
that actually this in the old school web
looking at this must have a electron
configuration of two four so we can see
two here closest In and four in the
outer well this must be carbon and if we
look at Carbon the ionization energy of
carbon is 1 S2 2 S2 2
P2 um and that fits perfectly we're
removing 2
P2
2p1 2 S2 and the 2 S1 and then we jump
into that next energy level and there's
our 1 S2 and our 1 S1 and that's a big
difference and you can see that huge
increase in uh in energy required to
remove that electron versus this
one um the other one that they quite
like in exams uh is this one and when
say they're quite like it has it's come
up once so it's not really as common as
certainly the others are um spot the
element that's uh this one down here
spot the element that has come up a few
times in the last few years so make sure
you can do that this one less so but I
quite like this anyway cuz it's it's
it's playing with Trends so it says use
your understanding of electron
arrangement to complete the table by
suggesting a value for the third
ionization energy of magnesium now
magnesium is 1 S2 2
S2 uh 2 p
six
3s2 now we know it has two electrons in
this outer shell this third shell here
then it has eight in the next one and
two in the final one so that means these
two are going to be increasing then we
know we're going to have a big jump to
this one
here big jump which means this should be
in line with these two which would be
basically this is going to be your uh
3s2 this is going to be your 3s1 this is
going to be the 2 P6 2 P5 and 2 P4 so
these we would expect a general Trend
again keep going then there'll be
another jump so big jump between this
and this in order to work this out you
actually can ignore these doesn't matter
it's these we were looking at and we say
well what's the difference between these
the difference between these is
1629 minus
10,500 which is roughly what uh
3,1 100ish yeah
3,129 so we got
3,129 going from there to there so the
way we work this out we'll just
take 3,129 off that and that gives us a
value of
7371 from just working that out now now
in the exam situation they were very
very generous and actually the answer
they were allowing anything from 5,000
to 9,000 which I think LS are a little
generous um and the actual value the
real value actually if you look it up is
77
32.7 and you can see just by following
this trend we actually get remarkably
close to that we're 400 away but that's
pretty close considering we've just
basically looked at the trend and worked
that out um and there you go so 73 71
bang in the middle almost of that that's
absolutely spawn you it's a perfect
answer
there that actually is it that's it for
ionization is really so
hopefully that has been of some help um
and it's if that kind of if these kind
of questions come up then hopefully you
are prepared for them um again any
comments um or requests or anything
stick them in the comments um and I hope
that's been some help
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