IGCSE Physics (2023-2025) - C22/25: The Nuclear Atom

Summary

This IGCSE physics video explores nuclear physics, focusing on the atom's nucleus. Initially, the Plum Pudding model was debunked by Rutherford's experiment, leading to the Solar System model. The video explains the nucleus as a dense concentration of protons and neutrons, called nucleons. It covers atomic structure, isotopes, and nuclear reactions like fission and fusion, highlighting mass-energy conversion through Einstein's E=mc² formula. The video promises to delve into radioactive particles in the next installment.

Takeaways

• 🔬 The video discusses the module of IGCSE physics known as Nuclear Physics, which focuses on the properties of the atomic nucleus and the reactions that occur within it.
• 🍮 The Plum Pudding model, an early atomic model, was disproved by Ernest Rutherford's gold foil experiment, which demonstrated that the atom has a small, dense, positively charged nucleus.
• 🔋 Alpha particles, consisting of two protons and two neutrons, were used in Rutherford's experiment, and their deflection indicated the presence of a concentrated positive charge within the atom.
• 🌐 The Solar System model of the atom emerged from Rutherford's findings, with a central nucleus containing protons and neutrons, and electrons orbiting around it.
• 🚩 Protons and neutrons are collectively known as nucleons and are located in the nucleus, while electrons orbit the nucleus.
• ⚖️ The relative mass of electrons is much less than that of protons and neutrons, which is why they have a negligible impact on the atom's overall mass.
• 📊 The number of protons determines the element's identity on the periodic table, and the atomic number is the sum of protons and neutrons.
• 🔄 Isotopes are variants of an element that have the same number of protons but different numbers of neutrons, resulting in different masses.
• 💥 Nuclear fission is a reaction where a heavy nucleus, like uranium, splits into smaller nuclei after absorbing a neutron, releasing energy and more neutrons.
• 🌟 Nuclear fusion is a process where light nuclei, such as hydrogen, combine to form a heavier nucleus, like helium, releasing a large amount of energy.
• ⚡ The mass defect observed in nuclear reactions is explained by Einstein's famous equation, E=mc^2, where lost mass is converted into energy.

Q & A

What is the main focus of Nuclear Physics in the context of IGCSE physics?

Nuclear Physics in IGCSE physics focuses on the properties of the nucleus of an atom and the reactions that occur within it.

What was the Plum Pudding model and why was it disproven?

The Plum Pudding model was an early atomic model that suggested the atom consisted of a positive 'pudding' with protons and electrons scattered within it. It was disproven by Ernest Rutherford's experiment, which demonstrated that the atom has a small, dense, positively charged nucleus.

What did Rutherford's experiment involve and what was the key observation?

Rutherford's experiment involved firing alpha particles at a thin piece of gold foil. The key observation was that while most alpha particles passed through, a few were deflected back, indicating a concentrated positive charge within the atom, which led to the discovery of the nucleus.

What is the Solar System model of the atom and how does it differ from the Plum Pudding model?

The Solar System model of the atom, also known as the Rutherford model, places a small, dense, positively charged nucleus at the center of the atom with electrons orbiting around it, similar to planets orbiting the sun. This differs from the Plum Pudding model, which suggested a uniform distribution of positive charge with electrons scattered throughout.

What are nucleons and what are their components?

Nucleons are the particles found in the nucleus of an atom, and they consist of protons and neutrons.

How does the number of protons in an atom determine its position in the periodic table?

The number of protons in an atom, also known as the atomic number, determines its position in the periodic table because it defines the element's identity. Elements are arranged in ascending order of atomic number.

What is the relationship between the nuclear number, proton number, and neutron number in an atom?

The nuclear number (also known as the mass number) is the total number of protons and neutrons in an atom. The proton number is the count of protons, and the neutron number can be found by subtracting the proton number from the nuclear number.

What are Isotopes and how do they differ from each other?

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. This results in different atomic masses but the same chemical properties.

What is nuclear fission and how does it occur?

Nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts, usually when struck by a neutron. This process releases energy and additional neutrons, which can lead to a chain reaction.

What is nuclear fusion and how does it differ from nuclear fission?

Nuclear fusion is a nuclear reaction where two light atomic nuclei combine to form a heavier nucleus, releasing a large amount of energy. It differs from nuclear fission in that fusion involves the combination of nuclei rather than their splitting.

How is the mass deficit in nuclear reactions accounted for according to Einstein's famous equation?

According to Einstein's equation, E=mc^2, the mass deficit in nuclear reactions is converted into energy. The lost mass (m) multiplied by the speed of light (c) squared gives the energy (E) released during the reaction.

Outlines

00:00

🔬 Introduction to Nuclear Physics

This segment introduces the topic of Nuclear Physics within the IGCSE physics curriculum. It explains the historical Plum Pudding model of the atom, which was later disproved by Ernest Rutherford's gold foil experiment. The experiment involved firing alpha particles at a thin sheet of gold and observing their deflection, which led to the discovery of the nucleus. The nucleus, a small, dense region at the center of an atom, contains all the positive charge and most of the mass of the atom, composed of protons and neutrons. The video also explains the Solar System model of the atom, where electrons orbit the nucleus, and provides a recap of the structure of an atom, including the roles of protons, neutrons, and electrons.

05:03

🧬 Atomic Structure and Isotopes

This section delves into the atomic structure, focusing on the nucleus and its components—protons and neutrons, collectively known as nucleons. The video explains the concept of isotopes, which are variants of an element with the same number of protons but different numbers of neutrons, resulting in different atomic masses. The nuclear number and proton number are introduced as tools to determine the number of neutrons in an atom. The video uses the example of calcium to illustrate this concept. It also touches on the properties of the nucleus, including its charge and mass, and how these relate to the number of protons and neutrons. The difference between nuclear fission and fusion is briefly introduced, setting the stage for further exploration in subsequent videos.

10:04

⚛️ Nuclear Reactions and Einstein's E=mc²

The final segment of the video discusses nuclear reactions, specifically nuclear fission and fusion, and their energy release. It explains the process of nuclear fission, where a uranium atom absorbs a neutron and splits into smaller elements, releasing energy and additional neutrons. This can lead to a chain reaction. The video also covers nuclear fusion, where two light nuclei combine to form a heavier nucleus, releasing energy. The famous equation E=mc² by Albert Einstein is introduced to explain the conversion of mass into energy during these reactions. The video concludes by summarizing the disproval of the Plum Pudding model, the study of atomic properties, and a teaser for the next video, which will explore radioactive particles.

Keywords

💡Nuclear Physics

Nuclear Physics is a branch of physics that studies the properties of atomic nuclei and the reactions they undergo. It is central to the video's theme as it sets the stage for understanding the experiments and models discussed, such as the Plum Pudding model and the Solar System model. The video delves into how our understanding of atomic structure evolved through experiments, leading to the current model of the atom.

💡Nucleus

The nucleus is the central part of an atom, containing protons and neutrons, and is the focus of nuclear physics. In the video, the concept of the nucleus is crucial for understanding the Rutherford experiment, which disproved the Plum Pudding model and led to the realization that the positive charge and most of the mass of an atom are concentrated in a tiny space at the center, the nucleus.

💡Plum Pudding Model

The Plum Pudding Model was an early atomic model that proposed a uniform 'pudding' of positive charge with electrons scattered within it, like plums in a pudding. The video explains how this model was disproved by Rutherford's experiment, which showed that the positive charge and mass of an atom are concentrated in a small nucleus, not distributed evenly.

💡Rutherford Experiment

The Rutherford Experiment is a pivotal experiment in nuclear physics, conducted by Ernest Rutherford. It involved firing alpha particles at a thin gold foil and observing their scattering. The video describes how this experiment led to the discovery of the nucleus, as it was found that a few alpha particles were deflected back, indicating a small, dense, positively charged center within the atom.

💡Alpha Particles

Alpha particles, consisting of two protons and two neutrons, are a type of ionizing radiation. In the video, they play a key role in the Rutherford Experiment, where their deflection provided evidence for the existence of the nucleus. The interaction of alpha particles with the gold foil demonstrated the presence of a concentrated positive charge within the atom.

💡Nuclear Fission

Nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts, releasing a large amount of energy. The video explains this process using uranium as an example, where absorption of a neutron leads to an unstable nucleus that splits, releasing energy and more neutrons, which can cause a chain reaction.

💡Nuclear Fusion

Nuclear fusion is the process of combining two light atomic nuclei to form a heavier nucleus, releasing energy in the process. The video contrasts this with fission, describing how in fusion, lighter elements like hydrogen combine to form helium, releasing energy and a neutron. This process is simpler than fission and is a key concept in understanding stellar nucleosynthesis.

💡Isotopes

Isotopes are variants of a particular chemical element which differ in neutron number, and thus in mass, while having the same number of protons. The video uses helium-4 and helium-3 as examples, explaining that isotopes of the same element have the same chemical properties but can differ in their physical properties due to the difference in neutron count.

💡Einstein's E=mc²

Einstein's famous equation E=mc² relates mass and energy, stating that mass can be converted into energy and vice versa. The video uses this equation to explain the mass defect observed in nuclear reactions, such as fission and fusion, where a small loss of mass corresponds to a significant release of energy, highlighting the immense energy potential in nuclear processes.

💡Subatomic Particles

Subatomic particles are the fundamental constituents of atoms, including protons, neutrons, and electrons. The video provides a detailed overview of these particles, discussing their masses, charges, and roles within the atom. Understanding these particles is essential for grasping the structure of the atom and the processes that occur within the nucleus.

Highlights

Introduction to the IGCSE physics module on Nuclear Physics.

Definition of the nucleus and its significance in atomic structure.

Historical context: The Plum Pudding model and its disproof.

Ernest Rutherford's experiment that led to the disproof of the Plum Pudding model.

Description of the Solar System model of the atom.

Explanation of how Rutherford's experiment disproved the Plum Pudding model.

The discovery of the nucleus as a concentrated positive charge within the atom.

Visual representation of Rutherford's findings on atomic structure.

Recap of the atom's structure according to the Solar System model.

Definition and properties of subatomic particles: protons, neutrons, and electrons.

Explanation of how the number of protons determines an element's identity.

Visualizing elements using the nuclear number and proton number.

Introduction to Isotopes and their significance in nuclear physics.

The concept that Isotopes share the same chemical properties but differ in mass.

Explanation of nuclear fission and its role in releasing energy.

The process of balancing nuclear reactions by conserving the number of nucleons.

The concept of chain reactions in nuclear fission.

Introduction to nuclear fusion and its energy release.

Einstein's famous equation, E=mc², and its application in nuclear reactions.

Summary of the video's key points on nuclear physics and a preview of the next topic: radioactive particles.

Transcripts

hello everyone in this video we're going

to look into another module of IGCSE

physics called The Nuclear Physics so

the word nucleus stems from the word

nucleus which means that this branch of

physics study what is the properties of

the nucleus of an atom and what are the

reactions that comes out from it so

initially scientists thought that

nucleus follows this model called The

Plum Pudding model so it is a disproof

model of the atom which imagine it to be

consists of a positive pudding like the

protons here and the electrons on the

other side so it's like a pluting and

how it is disproof is from this

experiment carried out by Ernest

ratafort so what they figure out is that

hey the atom should look like that so

this is also known as The Solar System

model of the atom and the experiment

that They carried out is this so what

Rutherford and the team does is that

they fire the alpha particles so alpha

particles is a particle of made up of

two protons and two neutrons

and at a very thin piece of goeth go for

so if the atom really follows the plum

pudding water right so it they should

they predict that the alpha particle

should pass straight through the goal

and what they found out is that most of

the particle pass straight through the

void as predicted and some of them they

deflected scarcely and a few of these

alpha particles they actually bounce

back towards the source of radiation

so what this experiment shows according

to Rutherford is that because alpha

particles are positively charged they

have two protons and if they are

repelled back from the Gopher is it must

be another positive charge remember

chapter 17 when we talk about electrical

repulsion so there must be another

positive charge

but what the experiments show is that

only a few are repelled and it shows

that the positive charge of the gold

atoms was concentrate in a tiny space

within the atom

and if not that would be a law of

deflection but then they found out that

only a few bounce back it shows that

protons in an atom is gathered around a

particular space

and the tiny curve concentrated positive

charge at the heart of every atom is

what we call today the nucleus the

nucleus of an atom and to show you an

image form of what Waterford explained

this is it

so they figure out that new there's

actually a tiny spot in an atom that

consists of all the positive charge

which is the nucleus that explains why

only a few of the alpha particle is

reflected directly back at the source

so in this image from this is what it

meant and again here's a recap on the

structure of an atom

um here we have nucleus in the middle

the Solar System model as what it's

shown by rather Fort they consist of

proton and also Neutron and we're now

looking to since we now have proved that

the structure of an atom follow the

Solar System model so we will

investigate it further so in the center

of the atom is the nucleus they have

proton and neutron

and the electrons is the one that is

surrounding the atom

so um by the way if you put together

proton and neutron they are known as

nucleons

so this table summarized the information

and masses and charges of the three

subatomic particles protonutrient

electrons so both protons and neutrons

that's in the nucleus whereas electrons

is orbiting the nucleus and as we

mentioned in chapter 17

proton has a charge of 1.6 times 10 to

the power of negative 19 column so its

relative charge is one as compared to

Neutron

and the mass of it is this amount and

you can see that new electrons here they

are heavier I mean they are less lighter

than proton and neutron so that's why

when you calculate relative mass so this

is the proportion of mass that electron

has that's compared to proton so that

suggests some properties of the three

subatomic particles

and if we look into atom what determines

the particular element in the periodic

table is the number of protons so if you

take chemistry you should be able to

notice and they are arranged in

ascending order in others accordance to

how many protons the atom has

and this is a way for us to visualize an

element so this is the helium element

and their first number notations here

first number stands for nuclear number

which is the amount of proton

plus the amount of nucleons Neutron

so two here stand for a proton number

they're not protons so in other words by

using this nuclear number and proton

number we can figure out how many

neutrons by using the nuclear number

minus the proton number so that's just a

very simple formula

and what can you deduce from whose the

atom whose nucleus can be represented by

this so this is a calcium we know that

they have 14 nucleon

and then six protons

so this shows us that there are six

protons here

oops let me use another color six

protons and because they have 14

nucleons mean that if you want to find

the number of neutrons you have to use

14 minus six therefore you get eight

Neutron

and also six electrons because we're

considering that this element is

um neutral meaning they have the same

amount of electrons and protons

so protons 14 and cloud and eight all

right so that's about it and when we

talk about elements some elements they

have something called the Isotopes

Isotopes means that they these elements

have the same number of protons making

them the same element but then

um they have sometimes different neutron

number that means they are heavier in

terms of their nucleus so for instance

helium-4 and helium-3 they have the same

number of protons but helium 4 will have

more neutrons so in other words they

have four nucleons so that's why name

nuclear force comes from again two three

five and two three eight uranium is the

same they have same proton number

different neutron number so these

Isotopes they have same chemical

properties because they have same number

of protons but then those with greater

number of neutrons is going to be

heavier

so the charge on the nucleus is equal to

the number of protons

so it has a relative charge of plus one

and the math of the nucleus is relative

equal to the mass of the nucleon as both

protons and neutron neutron has a

relative mass of one so go back to our

example just now if I have a uranium 235

it has a charge of plus 235 because

it has 92 plus 92 charge because it has

92 protons

and then for Uranium the mass will be

235 because that's the amount of nucleon

that it has

so when it comes to so now we have

studied the structure of an atom so

let's look into some of the reactions

that can occur in the nucleus of an

element first one is nuclear fission we

have already learned this in chapter

seven

and it happens when in uranium get hits

by a neutron

so the additional neutrons here will

make the uranium unstable

and therefore it will undergo precise

called nuclear fission

to two different elements here

and then with three again three neutrons

most importantly is the energy that they

release so that's um the formulas the

equation of nuclear fission you can see

that uranium gets hit by a neutron it

becomes this element plus this element

plus two Neutron plus some energy one

thing to note here is do you look at the

amount of protons before and sorry

nucleon before and after the equation

you'll find out that if you sum this up

you'll get 236 and after the equation

you will get the same number

also

236 so the number of protons and

neutrons before and after nuclear

reaction is going to be the same that's

also how you can balance it

great so um they said also lead to chain

reaction because all these elements here

they could be hit by another element

that leads to more reaction to happen

and that's what happened in nuclear

fission and as for nuclear fusion it's a

lot simple it's when two hydrogen

elements like different hydrogen

elements they combine together to form

helium plus a neutron plus a lot of

energy

all right so what scientists found out

is that for both nuclear fission and

nuclear fusion

the total mass of the particles here

particle Mass

before a fission or fusion reaction is

slightly more than after Direction

meaning the mass of this

math A1 and the mass of this here Mass 1

is greater than MS2 but if you think

about it where does the loss Mass go

like where's the all this Mass we

converted to and that leads us to the

famous Einstein formula called e equal

to MC square m stands for the mass that

is lost during the equation

and then C stands for the speed of light

then you power by two

and if you use the mass loss multiplied

by the speed of light Square you will

get the energy release which can be

super big

um so imagine that 1 kg is lost

multiplied by 3 times 10 to the power of

8 power of two that is a huge amount of

energy so that that is just a basic

summary of what the equation equal to MC

squared stands for so in this video we

show how the plant putting model is

first disproved by ratified experiment

then we also study

um the different properties of proton

electrons and neutron so that's it for

this chapter in the next video we'll

look into how this nuclear reaction will

release something called radioactive

particles and I'll see in the next video

thank you so much for watching