AQA A-Level Chemistry - Ionisation Energies

Summary

This 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

00:00

🔬 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.

05:01

📚 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.

10:03

📉 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.

15:04

🔍 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.

20:04

🗣️ 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.

Keywords

💡Ionization Energy

Ionization energy refers to the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous ions. This concept is central to the video's theme as it sets the stage for discussing the various factors that influence how easily an electron can be removed from an atom. The video script provides a clear definition and uses examples such as oxygen and magnesium to illustrate how ionization energy is calculated and its significance in chemistry.

💡First Ionization Energy

First ionization energy is the energy needed to remove the outermost electron from a neutral atom in its gaseous state to form a cation. The video emphasizes the importance of understanding first ionization energy by providing equations and examples, such as the ionization of oxygen and magnesium, to demonstrate the process and its relevance in determining an element's reactivity.

💡Second Ionization Energy

Second ionization energy is the energy required to remove an electron from a gaseous unipositive ion to form a gaseous dication. The video script explains this concept by differentiating it from the first ionization energy and providing an equation for the ionization of magnesium, which shows the increased energy needed to remove an electron from an already positively charged ion.

💡Charge of the Nucleus

The charge of the nucleus is a key factor affecting ionization energy. The video explains that a higher nuclear charge results in a stronger attractive force between the nucleus and the electrons, making it more difficult to remove an electron and thus increasing the ionization energy. This concept is illustrated by comparing the ionization energies of elements across the periodic table.

💡Distance from the Nucleus

Distance from the nucleus is another critical factor in determining ionization energy. Electrons that are further from the nucleus experience less attraction and are easier to remove, resulting in lower ionization energy. The video script uses this concept to explain trends in ionization energy within the periodic table, particularly the decrease in ionization energy as one moves down a group.

💡Shielding

Shielding refers to the effect where inner electrons shield the outer electrons from the full attractive force of the nucleus. The video script explains that increased shielding leads to a decrease in ionization energy because the outer electrons are less tightly held by the nucleus. This concept is used to discuss trends in ionization energy and the differences observed in elements within the same group of the periodic table.

💡Consecutive Ionization Energies

Consecutive ionization energies are the energies required to remove each electron sequentially from an atom. The video script uses graphs and examples to show how these energies increase with each removal and how significant jumps in energy correspond to moving from one energy level to another within an atom's electron configuration.

💡Periodic Trends

Periodic trends refer to the patterns in properties of elements as one moves across a period or down a group in the periodic table. The video script discusses how ionization energy increases across a period due to increasing nuclear charge and decreasing distance from the nucleus, and decreases down a group due to increasing atomic size and shielding.

💡Electron Configuration

Electron configuration is the distribution of electrons in an atom's orbitals. The video script uses electron configurations to explain how the arrangement of electrons affects ionization energy and to predict the energy changes when moving between different energy levels within an atom.

💡Gaseous Ions

Gaseous ions are atoms or molecules that have lost or gained electrons and exist in a gaseous state. The video script emphasizes the importance of specifying the state of matter when discussing ionization energy, as the definition and calculation of ionization energy specifically pertain to gaseous atoms and ions.

💡State Symbols

State symbols are used in chemistry to denote the physical state of a substance (solid, liquid, gas). The video script mentions the importance of including state symbols in chemical equations, particularly when discussing ionization energy, to accurately represent the conditions under which the ionization occurs.

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