OCR A 2.1.1 Atomic Structure and Isotopes REVISION
Summary
TLDRIn this educational video, Chris Harris from Allert Tutors explores atomic structure and isotopes as per the OCR specification. Harris explains the atom's components, including protons, neutrons, and electrons, and their charges and relative masses. He delves into ions, isotopes, and their differences, using oxygen as an example. The video also covers the historical development of atomic models, from Dalton's spherical atoms to Rutherford's nuclear model and Bohr's energy shells. Harris teaches how to calculate relative atomic mass using mass spectra, a method for measuring isotope masses, and identifies elements like chlorine and germanium through this process. The video is a valuable resource for students revising for exams, with supplementary PowerPoints available for purchase.
Takeaways
- 🔬 The video provides a revision overview of atomic structure and isotopes for the OCR specification.
- 🌐 The presenter, Chris Harris from allertutors.com, offers PowerPoints for purchase to aid in revision and note-taking.
- 💡 Atoms consist of a nucleus with protons and neutrons, and electrons orbiting in shells, with the nucleus being very small relative to the atom's size.
- ⚛️ Protons have a relative charge of +1 and mass of 1, neutrons have no charge and a relative mass of 1, and electrons have a charge of -1 and a very small relative mass.
- 📊 The periodic table lists elements with a mass number (larger number) indicating the sum of protons and neutrons, and an atomic or proton number (smaller number) indicating the number of protons.
- 🔋 The number of protons in an atom equals the number of electrons, and the number of neutrons can be calculated by subtracting the atomic number from the mass number.
- ⚡ Ions are atoms that have lost or gained electrons, resulting in a different number of electrons and protons, unlike neutral atoms.
- 🌐 Isotopes are variants of an element with the same number of protons but different numbers of neutrons, leading to different masses.
- 📈 The history of atomic models includes significant contributions from John Dalton, J.J. Thomson, Ernest Rutherford, and Niels Bohr, each refining the understanding of atomic structure.
- 🧬 Mass spectrometry is a technique used to measure the mass of isotopes in an element, and the relative atomic mass of an element can be calculated from the mass spectrum data.
Q & A
What is the main topic of the video presented by Chris Harris?
-The main topic of the video is the atomic structure and isotopes, specifically tailored for the OCR specification.
How can viewers obtain the PowerPoints used in the video?
-Viewers can purchase the PowerPoints by clicking on the link provided in the description box below the video.
What are the three main components of an atom as described in the video?
-The three main components of an atom are protons, neutrons, and electrons.
What is the relative charge and mass of a proton as mentioned in the video?
-A proton has a relative charge of plus one and a relative mass of one.
How does the video explain the difference between the number of protons and neutrons in determining the mass number of an element?
-The mass number of an element is determined by the sum of the number of protons and neutrons in the nucleus.
What is an ion according to the video?
-An ion is an atom that has lost or gained electrons, resulting in a different number of electrons and protons.
What is the key difference between isotopes as explained in the video?
-Isotopes are variants of an element with the same number of protons but different numbers of neutrons.
How does the video describe the historical development of the atomic model from John Dalton to Neils Bohr?
-The video outlines the progression from Dalton's solid sphere model, to Thomson's plum pudding model, Rutherford's discovery of the nucleus, and finally to Bohr's model with fixed energy shells.
What is the significance of the gold leaf experiment in the context of the video?
-The gold leaf experiment, conducted by Rutherford, provided evidence for the existence of a small, positively charged nucleus within the atom by observing the deflection of alpha particles.
How can the relative atomic mass of an element be calculated from its isotopes, as per the video?
-The relative atomic mass can be calculated by multiplying the mass of each isotope by its percentage abundance and summing these products, then dividing by the total percentage abundance.
What is the purpose of Mass Spectra as explained in the video?
-Mass Spectra is used to measure the mass of isotopes in an element by determining the mass-to-charge ratio of the ions produced when electrons are removed from the atoms.
Outlines
🔬 Atomic Structure and Isotopes Overview
This paragraph introduces the video's focus on the OCR atomic structure and isotopes, presented by Chris Harris from Allert Tutors. The video aims to provide a revision overview based on the OCR specification. Chris mentions that the PowerPoint slides used in the video are available for purchase, which can be beneficial for revision on various devices. The content is structured around the specification points, starting with an explanation of the atom's structure, including protons, neutrons, and electrons, and their relative charges and masses. The paragraph emphasizes the importance of understanding the atomic structure, specifically the relationship between protons, neutrons, and electrons in an atom, and how to calculate the number of neutrons. It also touches on the concepts of ions and isotopes, explaining the difference between atoms and ions, and how isotopes vary in neutron numbers while maintaining the same number of protons.
📚 Historical Development of Atomic Models
This paragraph delves into the historical development of atomic models, starting with John Dalton's 1803 proposal of atoms as solid spheres of different sizes. The narrative progresses to JJ Thomson's 1897 'plum pudding' model, which introduced the concept of electrons within an atom. Ernest Rutherford's 1909 model is then discussed, highlighting his discovery of the nucleus and the atom's mostly empty space. The paragraph concludes with Neils Bohr's 1913 model, which introduced the idea of fixed energy shells for electrons, solving the issue of electron collapse towards the nucleus. This historical overview provides context for the evolution of our understanding of atomic structure.
🧪 Understanding Isotopes and Mass Spectra
The final paragraph discusses the concept of isotopes, which are variants of an element with different numbers of neutrons, resulting in different masses while sharing the same number of protons. It explains the use of mass spectrometry to measure the mass of isotopes, detailing the process where elements lose an electron and form a positive charge. The paragraph describes how mass-to-charge ratios (m/z) are used to determine the mass of isotopes, with the majority of ions forming a +1 charge. It explains the concept of percentage abundance, which represents the proportion of each isotope in a sample. The paragraph concludes with an example of calculating the relative atomic mass of an element using the abundance and mass of its isotopes, illustrating the process with chlorine and germanium as examples. This section provides a practical understanding of how isotopes are identified and their masses determined.
Mindmap
Keywords
💡Atomic Structure
💡Isotopes
💡Protons
💡Neutrons
💡Electrons
💡Ions
💡Atomic Number
💡Mass Number
💡Relative Atomic Mass
💡Mass Spectra
💡Periodic Table
Highlights
Introduction to atomic structure and isotopes for OCR specification.
Availability of PowerPoints for purchase to aid in revision.
Explanation of the atom's composition including protons, neutrons, and electrons.
Description of the relative charges and masses of subatomic particles.
Importance of the number of protons and electrons in determining atomic structure.
Calculation method for determining the number of neutrons in an atom.
Definition and example of ions, including their formation and charge.
Explanation of ionic bonding and its role in forming stable compounds.
Introduction to isotopes, their definition, and how they differ from ions.
Discussion on the isotopes of carbon and their varying neutron counts.
Historical overview of atomic models, starting with John Dalton's spherical atoms.
JJ Thomson's plum pudding model and the discovery of the electron.
Ernest Rutherford's gold foil experiment and the discovery of the nucleus.
Niels Bohr's model of fixed energy shells and its significance.
Modern atomic model with subshells and its implications for ionization trends.
Definition of relative atomic mass and its calculation using isotopes' abundance.
Explanation of mass spectrometry and its use in measuring isotopes' mass.
Method for calculating relative atomic mass from mass spectrometry data.
Identification of elements using their relative atomic mass from the periodic table.
Conclusion and call to action for subscribing to the channel and purchasing PowerPoints.
Transcripts
[Music]
hello and welcome to this video uh this
is the OCR atomic structure and Isotopes
revision video uh my name is Chris
Harris I'm from allert tutors.com uh and
in this video like I say we're going to
go through the just give you a quick
overview of the atomic structure and
Isotopes part for the OCR specification
um the Powerpoints that I'm using here
um you can um purchase these PowerPoints
if you just click on the link in the
description box below this video be able
to get them there they' be great for
things like revision um adding to your
notes Etc you can use them um on your
phone and the tablet and the way to
school or college or anything so
there'll be um there's just another way
another bit of material for you to
revise from all right like I say these
things are based on the specification so
as you can see obviously these are the
spef spe ification points um and this
one is directly linked to the OC
specification okay so um just to remind
you as well this one's from module two
obviously this bit here okay so it
starts off looking at the atom okay so
we need to know the structure of the
atom the atom is made of protons and
neutrons as you can see in the middle
here they're really small relative to
the full size of the atom we have
negative electrons orbiting round in
shells and these take up most of the
space of an atom the charges of these
things proton is a relative charge at
plus one its mass is one relative mass
the neutron zero it's relative mass is
one this is basically just the the mass
relative to each other and electron has
got a charge of minus one uh and its
relative mass is 1 over 2,000 you can't
just put zero because electron does have
a mass it's just very very small um you
can probably remember these as uh proton
positive proton for positive charge
Neutron neutral for neg for neutral
charge so um you could probably um
remember it in that way okay obviously
in the periodic table you have your
elements and you have two numbers in
these elements here the top number uh or
sometimes it might be the other side
actually so we'll say the bigger number
the bigger number is called the mass
number uh it tells us the number of
protons and neutrons in the nucleus uh
and the smaller number tells us the it's
called the atomic or the proton number
and this basically just tells us the
number of protons in the nucleus um and
also in atoms as well it's really
important to know that the number of
protons equals the number of electrons
in atoms and if you wanted to work out
the number of neutrons all we do is you
subtract your 7 minus 3 and obviously
that will tell you the number of
neutrons in an
atom okay so let's look at ions and
Isotopes so ions are um basically atoms
that have lost or gained electrons um
and they have a different number of
electrons and protons they're not the
same unlike in atoms so for example
here's oxygen oxygen is in in group uh
six it has six electrons in its outer
shell um so to gain a full shell of
electrons um it would need an extra two
electrons to get the full eight and then
it would attract to a positive charge to
form a stable compound um we can see
oxygen here oxygen is eight protons with
a charge of plus eight eight neutrons
obviously that doesn't have a charge and
the ion has 10 electrons charge of min-2
so if we do do Min - 10 plus 8 that
gives a total charge of- two so um this
is obviously a negative charge and this
would bond to something that's
positively charged something like sodium
uh it has 11 protons charge of + 11 12
neutrons no charge 10 electrons its
charge is minus 10 obviously because
it's got one more proton than it does
electron its total charge is+ one these
two can OB you bond together and form a
much more stable compound um so that's
pretty pretty useful and you see them a
lot that's an ionic
bond right isops are a little bit
different so these are elements with the
same number of protons they have a
different number of neutrons okay so
this is going to make it um obviously a
little bit heavier each of the Isotopes
so let's have a look at these Isotopes
here these are three different types of
carbon 12 um and um three different
types of carbon isotop sorry we have
carbon 12 carbon 13 carbon 14 uh and
obviously we've got the the proton
number or the atomic number on the
bottom now what I've done is I've
written down the uh number of protons
neutrons and electrons in each one of
these
um and there's some things that we need
to point out so if you look on the top
one these things have the same number of
protons all of these do but the number
of neutrons is different if you look
we've gone from six neutrons here seven
neutrons here eight neutrons here okay
so these are called Isotopes so make
sure you'll be able to recognize
them okay we need to know about the
history of the atom as well how the atom
has developed over time so we've got
this timeline here we're going to start
way back in 1803 John Dalton he came up
with the IDE idea of spheres he said
that all atoms were spheres uh and he
just had different types of spheres
different sizes and that's basically
what he come up with so he had a first
go with it obviously we don't we know
this is not true now um but back then it
was accepted and until we had in
1897 so um just over 90 years later we
had JJ Thompson uh he had another go and
he kind of amended John Dalton's idea uh
and came up with a new model uh
basically he discovered the electron uh
he said the atom wasn't solid uh and was
made up of other particles and he called
it the plum pudding model so he said
that he had negative uh negative
electrons which are these yellow circles
here and we had the positive pudding bit
so um I have no idea what a plum P would
look like but obviously it must look
something like this um so he basically
came up with this idea and he tried to
explain um his model obviously in a more
um less abstract Way by coming up with
the word plum pudding
uh a little bit later on 1909 Ernest
Rutherford okay so he developed
Thompson's idea it wasn't so much of a
gap now he discovered the nucleus and he
said that actually this nucleus is
really small uh and it was positively
charged and he he basically said it was
really small compared to the rest of the
atom he said it was mainly empty space
and it was made of some negative Cloud
he said so it was just like a cloud of
negative stuff around a positive um very
small nucleus and he had some evidence
actually to back this up um he used a
gold leaf experiment and basically what
he did is he fired alpha particles at a
thin bit of gold leaf most of them went
through um which suggested that most of
the at was empty space um some of them
were deflected which means they were
kind of because alpha particles were
positively charged they deflected away
from the nucleus that told them it must
have been a positive nucleus and some
very very very few bounced straight back
towards where the alpha part were being
fired at and he but basically suggested
that this nucleus was absolutely tiny
because not many of them were actually
being completely uh fired back at him so
basically that was his evidence and he
used this gold leaf
experiment uh a little bit later on 1913
Neils B right he said well actually
there's an issue with this there's a
problem he said how can you have a cloud
of electrons around a positive nucleus
The Cloud of electrons just collapse cuz
obviously nucleus was positive and the
electrons were negative so they would
attract each other it just collapse into
the atom so what he said was he said
actually um we must have something else
and not something else was fixed energy
shells so Neil's B came up with the idea
of energy shells so this was the model
that we getting bit little bit more
familiar with now so and actually he
could prove it he said when the EM
radiation is absorbed so this is
electromagnetic radiation the electrons
can move between the shells and when
they do that they emit this radiation
when the electrons move down to lower
shells and he measured um this um this
kind of emission that was coming from
the atoms and the only way you could
describe this was using this shell
Theory you couldn't do it with a cloud
model so um that's pretty uh that's
pretty
important okay the atomic model today
obviously electrons don't have the same
energy in the shells obviously nowadays
we now we've got now we know that we've
got subshells um and this basically
explains the ionization Trends okay so
the trend
um which we'll see um later on in this
in this module okay so obviously we know
got subshells like P SD subshells
Etc okay your definitions right you
really do need to know these definitions
apart from this bottom one in the red
but you do need to know all the rest of
them so we've got let's have a look at
this blue one this is called the
relative atomic mass okay or the a
basically this is the weighted mean mass
of an atom uh of an element compared to
1 12th of the mass of a carbon 12 atom
so um this is basically the uh the uh
the mass of something like an atom for
example the relative isotopic mass this
is the mass of an atom of an isotope
compared to 1 12th of the mass of an
atom of carbon 12 so this is basically
the mass of an isotope that makes it up
notice they're kind of they're very
similar in terms of um 112th of the mass
of at of carbon 12 very very important
and Rel to molecular mass um this might
be a bit useful you don't have to
remember this definition um for OCR but
it's just the mean mass of a molecule
compared to 1 12th of the mass of an
atom carbon 12 basically everything was
measured uh against carbon 12 okay so um
that was like the reference uh element
that they used hence the word
relative okay so let's look at Mass
Spectra so Mass Spectra is a way in
which we can measure the um the mass of
Isotopes in an element and just want to
kind of walk you through the the graph
and show you what we've got here okay so
looking at the bottom here this is
called the MZ the MZ is the mass to
charge ratio um basically this is the
mass of the isotope divided by its
charge now when it goes to a mass
spectrometer the elements lose an
electron and and when they lose this
electron obviously they form a positive
charge now most of the time the vast
majority of the time only one electron
is knocked off so we only form one plus
charge so when we do the mass of the
isotop divided by one we just get
literally the mass of the isotope so
most of it is plus one charge and this
is basically the same as the isotopic
mass so for example 37 is the MZ here we
can basically assume that is the mass of
the isotop as well or the relative mass
along theide here's percentage abundance
this is given as a percentage uh
abundance of the isotope in the sample
so obviously abundance is the amount of
something so the higher the abundance
the more of it you got um sometimes it's
shown as a percentage in which case it
be out of 100 sometimes it might be a
nominal value so it'll just be called
relative abundance in which case you
just add up all the Isotopes and that'll
tell you obviously what to divide it by
which you'll show see in a minute okay
so the must add up to give 100 there we
go 75 we only got two isops here 75% 25%
so they add up to
100 okay this Spectra like I say shows
two isotopes we've got one element but
two isops 75% of isops with a mass of 35
20 25% of the Isotopes with a mass of 37
so this is assuming they all have a one
plus charge obviously that's the
Assumption we're taking and most of them
will and so from this actually we can
work out the relative atomic mass and
we're going to have a look at that
next okay so let's have a look how we
can work this out so the relative atomic
mass can be worked out by taking the
abundance of a multiplied by the m to
charge of a plus the abundance of B
Times by the mass the charge of B Etc so
here we've only got two ice TOS but if
you had three or four or five you
literally just repeat these bits and
just keep adding them up divide it by
the total abundance now in this case the
abundance is percentage so it's out of
100 but yours might not be and yours
might be a relative abundance in which
case you just add the total abundance
for each ice toop and put that number at
the bottom there in this case we're
using percentage so relative uh relative
atomic mass 75 * 35 which is that time
that 25 * 37 which is 25 * 37 multiply
them two divid it by 100 cuz it's a
percentage abundance and we should get
35.5 we can use the periodic table and
we can identify the element as chlorine
if you look at the period table you
should see the mass that has 35.5 is
chlorine so pretty useful
actually right this is a different way
of doing it uh this is just using one
with a table again we just got Isotopes
and we've got abundance uh you see we've
got a few isops in this one um and we
got the abundance of each again it's out
of a percentage so let's have a look
relative atomic Mass 70 * 20.5 time uh
plus 72 + 27.4 blah blah blah right all
the way along basically we're just
multiplying these two that times that
plus that times that plus that times
that Etc all the way along divid it by
100 because it's a percentage abundance
so that's the total amount now if we put
that in our calculator we should get the
answer to be
72.6 and again if we look in the
periodic table we should be able to
identify the element as germanium or GE
so you can check that out and have a
look on the periodic
table and that's it that is um the
little quite small topic on atomic
structure and isops um please remember
to subscribe to my channel if you just
click on um the middle button uh right
now um and remember you can purchase
these uh PowerPoints if you like from
the link in the description box just
click on that link there and you can get
a hold of them great for vision all
right that's it now bye-bye
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