GCSE Chemistry - Elements, Isotopes & Relative Atomic Mass #2

Summary

This educational video script explains the structure of an atom, highlighting the central role of protons in determining an element's identity. It introduces the periodic table, nuclear symbols, and atomic numbers. The concept of isotopes is explored, emphasizing their identical chemical properties despite varying neutron counts. The script further delves into calculating the relative atomic mass of elements, using copper as an example to illustrate the process of averaging isotope masses based on their abundance.

Takeaways

• 🔬 Atoms consist of a central nucleus with protons and neutrons, and electrons orbiting around it.
• 🌐 The number of protons in an atom's nucleus determines the element it is.
• ⚛️ Hydrogen is the smallest element with one proton, while helium has two protons and two neutrons.
• 📊 The periodic table organizes elements, with each box representing a different element and its atomic number.
• 🔢 The atomic number, found at the bottom left of a periodic table box, is unique to each element and represents the number of protons.
• 🔤 Nuclear symbols represent elements with one or two letters, and the periodic table often includes both the symbol and the element's name.
• 🌀 Isotopes are different forms of the same element that have the same number of protons but different numbers of neutrons.
• 💠 Carbon-12 and Carbon-13 are isotopes of carbon with six and seven neutrons respectively, affecting their mass numbers.
• 🧮 The relative atomic mass (Ar) of an element is calculated by averaging the masses of its isotopes, weighted by their abundances.
• 📖 To calculate the relative atomic mass, multiply each isotope's abundance by its mass, sum these products, and divide by the total abundance of all isotopes.

Q & A

What is the central part of an atom called, and what does it consist of?

The central part of an atom is called the nucleus, which consists of protons and neutrons.

How does the number of protons in an atom's nucleus determine the element?

The number of protons in an atom's nucleus determines the element because each element has a unique atomic number, which is the number of protons in its atoms.

What is the smallest element, and how many protons does it have?

The smallest element is hydrogen, which has one proton in its nucleus.

What is the significance of the atomic number in the periodic table?

The atomic number in the periodic table is significant because it represents the number of protons in the atoms of an element, which uniquely identifies the element.

What is the difference between an element and its isotopes?

Isotopes are different forms of the same element that have the same number of protons but a different number of neutrons.

How do isotopes affect the chemical properties of an element?

Isotopes do not affect the chemical properties of an element because chemical properties are determined by the number of electrons, particularly the electrons in the outermost shell, which remains the same across isotopes.

What is the mass number of an isotope, and how is it calculated?

The mass number of an isotope is the total number of protons and neutrons in its nucleus, calculated by adding the number of protons (atomic number) to the number of neutrons.

How is the relative atomic mass of an element calculated, and why is it important?

The relative atomic mass of an element is calculated by summing the products of each isotope's abundance and mass, then dividing by the sum of the abundances of all isotopes. It is important because it represents the average mass of an atom of that element as found in nature.

What does the abundance of an isotope represent?

The abundance of an isotope represents how common or rare that isotope is in nature, indicating the percentage of all atoms of an element that are of that particular isotope.

Can you provide an example of how to calculate the relative atomic mass using the script's information on copper?

Yes, the relative atomic mass of copper can be calculated by multiplying the abundance of each isotope (69.2% for copper-63 and 30.8% for copper-65) by their respective mass numbers (63 and 65), summing these products, and then dividing by the total abundance (100%). The calculation is (69.2 * 63 + 30.8 * 65) / 100, which results in a relative atomic mass of approximately 63.6.

Outlines

00:00

🔬 Atoms and the Periodic Table

This paragraph introduces the structure of an atom, which consists of a central nucleus made up of protons and neutrons, with electrons orbiting around it. The number of protons in the nucleus determines the element, with hydrogen being the smallest element having one proton and one electron. The periodic table organizes elements into boxes, each representing a unique element with its atomic number indicated at the bottom left, which is the number of protons. The video also explains nuclear symbols, which are one or two-letter representations of the element names. Isotopes are introduced as different forms of the same element with the same number of protons but varying numbers of neutrons. Carbon is used as an example to illustrate isotopes, such as carbon-12 and carbon-13, which differ in their neutron count but chemically behave similarly.

05:02

📊 Calculating Relative Atomic Mass

The second paragraph delves into the concept of relative atomic mass (denoted as 'ar'), which is the average mass of all isotopes of an element. It uses copper as an example, explaining that copper has two stable isotopes: copper-63 and copper-65, with abundances of 69.2% and 30.8%, respectively. The calculation of relative atomic mass is demonstrated through a formula that involves multiplying the abundance of each isotope by its mass and then dividing by the total abundance of all isotopes. The calculation shows that the relative atomic mass of copper is approximately 63.6 when rounded to one decimal place. The paragraph concludes with a reminder of the importance of understanding this concept for exams and further study.

Keywords

💡Atom

An atom is the basic unit of matter, consisting of a central nucleus containing protons and neutrons, surrounded by electrons in orbit. In the video, the atom's structure is used to explain the composition of elements, with the number of protons in the nucleus determining the element's identity. For instance, hydrogen has one proton, making it the smallest element, while helium has two protons.

💡Nucleus

The nucleus is the central part of an atom, composed of protons and neutrons. It is the focus of the video's discussion on atomic structure, as it contains the protons that define the element. The video uses the nucleus to differentiate between elements, such as hydrogen with one proton and helium with two.

💡Proton

A proton is a subatomic particle with a positive electric charge found in the nucleus of an atom. The video emphasizes that the number of protons determines the type of element, as each element has a unique number of protons. For example, carbon has six protons, which is its defining characteristic.

💡Neutron

A neutron is a subatomic particle with no electric charge, also found in the nucleus of an atom. While the number of protons defines the element, the number of neutrons can vary among atoms of the same element, leading to different isotopes. The video uses neutrons to explain the concept of isotopes, such as carbon-12 and carbon-13.

💡Electron

Electrons are negatively charged subatomic particles that orbit the nucleus of an atom. The video mentions electrons in the context of the atom's overall structure, noting that they are present in numbers equal to the number of protons to maintain electrical neutrality, such as in hydrogen with one electron.

💡Element

An element is a substance that is made up of atoms with the same number of protons. The video explains that elements are the fundamental building blocks of matter, and their identity is determined by the number of protons. The periodic table organizes elements based on this atomic number, as exemplified by hydrogen and helium.

💡Periodic Table

The periodic table is a chart that organizes elements based on their atomic number, which is the number of protons in an element's nucleus. The video uses the periodic table to illustrate the organization of elements and to identify elements by their atomic numbers, such as lithium with an atomic number of three.

💡Isotopes

Isotopes are variants of an element that have the same number of protons but different numbers of neutrons. The video explains isotopes as different forms of an element, like carbon-12 and carbon-13, which have the same chemical properties but different masses due to the varying number of neutrons.

💡Atomic Number

The atomic number is the number of protons in the nucleus of an atom, which uniquely identifies the element. The video emphasizes the importance of the atomic number in determining the element, as seen with helium having an atomic number of two, making it distinct from other elements.

💡Relative Atomic Mass

The relative atomic mass is the average mass of all the isotopes of an element, taking into account their abundance. The video demonstrates how to calculate the relative atomic mass of copper by multiplying the abundance of each isotope by its mass and then dividing by the total abundance, resulting in an average mass that represents the element.

💡Abundance

Abundance refers to the proportion of each isotope within a naturally occurring element. The video uses copper as an example, explaining that copper-63 makes up 69.2% of naturally occurring copper, while copper-65 makes up 30.8%, which is crucial for calculating the relative atomic mass.

Highlights

An atom consists of a central nucleus with protons and neutrons, and electrons orbiting around it.

The number of protons in an atom's nucleus determines the element it is.

Hydrogen is the smallest element with one proton and one electron.

Helium is the next smallest element with two protons, two neutrons, and two electrons.

There are approximately 100 different elements organized into the periodic table.

Each box in the periodic table represents a different element with a unique atomic number.

The atomic number represents the number of protons in an atom and defines the element.

Isotopes are different forms of the same element with the same number of protons but different numbers of neutrons.

Carbon-12 and Carbon-13 are examples of isotopes of carbon with different numbers of neutrons.

Isotopes have the same chemical properties but different masses due to varying numbers of neutrons.

The relative atomic mass is the average mass of all isotopes of an element.

Copper has two stable isotopes, Copper-63 and Copper-65, with different abundances.

The relative atomic mass is calculated by multiplying isotope abundance by isotope mass and dividing by the sum of all abundances.

The relative atomic mass of copper is approximately 63.6 to one decimal place.

The symbol for relative atomic mass is 'ar', indicating the average mass of an element's atoms.

The video provides a comprehensive explanation of atomic structure, isotopes, and relative atomic mass calculation.

Transcripts

as we saw in our last video an atom is

made up of a central nucleus which

comprises protons and neutrons

and then has electrons orbiting that

nucleus we also saw that it's the number

of protons that tells us which element

it is

the smallest element is hydrogen

as its atoms have just one proton in

their nucleus with one electron orbiting

it

the next smallest is helium

whose atoms have two protons and two

neutrons in the nucleus

and then two electrons orbiting them

in total there are around 100 different

elements

and they've been organized into the

periodic table

with each box representing a different

element

we call these boxes nuclear symbols as

we saw in the last video

and the number in the bottom left is the

atomic number

which is unique to that element

as it represents the number of protons

in the atoms of that element

and any atom with that many protons must

be that element

so our atom here which has two protons

must be helium

because helium's atomic number is two

or if we take carbon we can see that its

atomic number is six so all carbon atoms

have six protons

so if we found an atom with three

protons like this one here

then it couldn't be carbon

we'd have to find the element with an

atomic number of three

which if we check the periodic table is

lithium

another feature of nuclear symbols is

the one or two letter symbol that

represents the element name

so c stands for carbon

and li means lithium

some symbols though are a bit more

confusing

for example sodium is n a

and iron is fe

most predict tables have both the symbol

and the name though so if you're not

sure what a certain symbol is you can

just find on the periodic table and

check

so now that we know that it's a number

of protons that determines which element

it is

what about the number of neutrons

well the number of neutrons can actually

vary between the individual atoms of an

element

as long as the number of protons remains

the same it's still the same element

and we call these different forms of

that element isotopes

the definition which you need to

remember is isotopes are different forms

of the same element

that have the same number of protons but

a different number of neutrons

let's take a look at carbon to show you

what we mean

the most common form of carbon is

so-called carbon-12

which has six protons six neutrons and

six electrons

a rare reform is the isotope carbon 13

which of course still has six protons

because it's carbon

but has seven neutrons and 6 electrons

this means that it has a mass number of

13 rather than 12

which is why we call it carbon 13.

because isotopes only vary in the number

of neutrons they have chemically they

all react in basically the same way

now because they all have different

numbers of neutrons the different

isotopes will have different masses

and one of the things that you need to

be able to do is calculate the average

mass of all the isotopes that make up a

particular element

which we call the relative atomic mass

let's take a look at copper as an

example

now copper has two stable isotopes

copper 63 which has an abundance of 69.2

percent

and copper 65 which has an abundance of

30.8

and when we say abundance all we mean is

how common or rare that isotope is

so if you were to pick up a handful of

copper

then on average 69.2 percent of the

atoms in your hand would be the copper

63 isotope

and the other 30.8 percent would be the

copper 65 former

now in an exam you might get a question

like calculate the relative atomic mass

of copper to one decimal place

the equation for relative atomic mass

is a sum of isotope abundance times

isotope mass

divided by the sum of the abundances of

all the isotopes

so the first thing we do is multiply

each isotope's abundance by its mass

so for the copper 63 isotope this would

be 69.2

which is its abundance

times 63 which is its mass

and for copper 65 it would be 30.8 times

65

then we sum these two figures together

which just means we add them together

lastly we divide this by the sum of the

abundances of all the isotopes

which in this case would be 69.2

plus 30.8

now you can either put this all straight

into your calculator

or simplify it down first

69.2 times 63 gives us 4359.6

while 30.8 times 65 gives us 2002

and then we add these together to get

6361.69

on the bottom 69.2 plus 30.8 gives us

100

which makes sense because there are only

two isotopes

so together they should add up to 100

so that they represent all of the copper

atoms

so we divide 6361.69

by 100 and our answer is 63.6169

but as the question asks for one decimal

place we give the answer as 63.6

and this number that we found is the

relative atomic mass

which is denoted by the symbol ar

so we could say that the average mass of

a copper atom is

63.6 anyway that's all for this video so

if you found it useful then please do

share with your friends or give us a

comment down below and we'll see you

next time