A Level Chemistry Revision "Electron Configuration"

Summary

This educational video script from the 'Three Science' series teaches viewers how to determine electron configurations of elements. It explains the concept of atomic orbitals, subshells, and the energy levels associated with them. The script outlines three key rules for electron assignment: filling the lowest energy orbitals first, allowing two electrons per orbital with opposite spins, and distributing electrons across degenerate orbitals before pairing. Examples are provided, starting with hydrogen and helium, then challenging viewers to determine lithium's configuration and finally nitrogen's, which has seven electrons. The script promises to explore more complex examples and exceptions in a subsequent video.

Takeaways

• 🔬 The video is a chemistry lesson focused on electron configuration in elements.
• 🌐 An atomic orbital is a region around the nucleus where up to two electrons with opposite spins can reside.
• 📚 There are different types of orbitals: s, p, d, and f orbitals, each with unique characteristics.
• 📈 Subshells, which are groups of orbitals of the same type in the same shell, have varying energies.
• 📉 The energy of subshells increases as we move away from the nucleus.
• ✅ Three key rules for assigning electrons to orbitals are: fill the lowest energy orbitals first, each orbital can hold two electrons with opposite spins, and distribute electrons into individual orbitals before pairing when energies are the same.
• 💡 The video provides examples of how to assign electrons to orbitals, starting with hydrogen and helium.
• 🚀 Electron configuration is a shorthand notation that represents the distribution of electrons in an atom's subshells.
• 🌿 The example of nitrogen is used to illustrate how to determine electron configuration, which for nitrogen is 1s² 2s² 2p³.
• 🔍 The video concludes with a teaser for the next part, which will cover more complex examples and exceptions to the rules of electron configuration.

Q & A

What is an atomic orbital?

An atomic orbital is a region around a nucleus where electrons are most likely to be found and can hold up to two electrons with opposite spins.

What are the different types of orbitals mentioned in the script?

The different types of orbitals mentioned are s, p, d, and f orbitals.

What is a subshell in the context of atomic orbitals?

A subshell consists of all orbitals of the same type within the same shell, such as the 3d subshell shown in the script.

How does the energy of subshells change as we move away from the nucleus?

As we move away from the nucleus, the energy of the subshells increases.

What are the three rules for assigning electrons to atomic orbitals?

The three rules are: 1) Orbitals with the lowest energy are filled first. 2) Up to two electrons with opposite spins can occupy the same orbital. 3) If orbitals have the same energy, electrons are placed in individual orbitals before pairing them.

How is the electron configuration of hydrogen represented in the script?

The electron configuration of hydrogen is represented as 1s1, indicating one electron in the 1s subshell.

Why do electrons in the same orbital have opposite spins?

Electrons in the same orbital must have opposite spins due to the Pauli Exclusion Principle, which states that no two electrons in an atom can have the same set of quantum numbers.

What is the electron configuration for helium as described in the script?

The electron configuration for helium is 1s2, indicating two electrons in the 1s subshell with opposite spins.

How does the script describe the electron configuration for lithium?

The electron configuration for lithium is 1s2 2s1, showing the first two electrons in the 1s subshell and the third electron in the 2s subshell.

What is the process for assigning the remaining electrons to orbitals in nitrogen as per the script?

For nitrogen, the first two electrons go into the 1s subshell, the next two into the 2s subshell, and the remaining three electrons go into the 2p subshell, with the electron configuration being 1s2 2s2 2p3.

Why are individual orbitals in the 2p subshell not shown in the electron configuration?

Individual orbitals in the 2p subshell are not shown in the electron configuration because it only represents the subshells, not the individual orbitals within them.

Outlines

00:00

🔬 Electron Configuration Basics

This paragraph introduces the concept of electron configuration in elements, building on the understanding of atomic orbitals established in a previous video. It explains that different subshells have different energies and that electrons fill the lowest energy orbitals first. The video script outlines three key rules for assigning electrons to atomic orbitals: 1) filling the lowest energy orbitals first, 2) allowing up to two electrons per orbital with opposite spins, and 3) distributing electrons into individual orbitals before pairing them when orbitals have the same energy. Examples are given to illustrate these rules, starting with hydrogen and helium, and then moving on to lithium, which has its third electron placed in the 2s orbital of the second shell. The paragraph concludes with an exercise for the viewer to draw the electron configuration for nitrogen, which has seven electrons.

Keywords

💡Atomic Orbital

An atomic orbital is defined as a region surrounding the nucleus of an atom where electrons are most likely to be found. In the context of the video, the concept of atomic orbitals is fundamental to understanding how electrons are distributed around the nucleus. The video explains that different types of orbitals exist, including s, p, d, and f orbitals, and these are part of subshells within electron shells.

💡Subshell

A subshell is a group of atomic orbitals that have the same shape and energy level within an electron shell. The video script mentions 3d subshell as an example, emphasizing that subshells are crucial for determining the arrangement of electrons in atoms. The energy of subshells increases as one moves away from the nucleus.

💡Electron Configuration

Electron configuration refers to the distribution of electrons in an atom's orbitals. The video script uses this term to describe the step-by-step process of assigning electrons to different atomic orbitals. For example, the electron configuration of hydrogen is given as '1s1', indicating one electron in the 1s subshell.

💡Electron Spin

Electron spin is an intrinsic property of electrons, which can be thought of as them spinning on their axes. The video script explains that each orbital can hold two electrons with opposite spins. This is important for understanding the Pauli Exclusion Principle, which is not explicitly mentioned but implied in the discussion of electron placement.

💡Energy Levels

Energy levels, in the context of the video, refer to the different potential energies that electrons can have within an atom. The video script illustrates that as one moves away from the nucleus, the energy of subshells increases, which is a key principle in understanding electron distribution.

💡Pauli Exclusion Principle

Although not explicitly named in the script, the Pauli Exclusion Principle is implied when discussing that an orbital can hold a maximum of two electrons with opposite spins. This principle is fundamental to understanding why electrons fill orbitals in the way they do, as explained in the video.

💡Hund's Rule

Hund's Rule is mentioned indirectly in the script when discussing that electrons fill individual orbitals before pairing up. This rule states that electrons will occupy separate orbitals in the same subshell with the same spin before pairing up, maximizing the total spin of the atom.

💡Electron Shells

Electron shells are the layers or 'shells' in which subshells and orbitals are located. The video script uses the term to describe the different energy levels at which electrons reside, such as the first shell (1s) and the second shell (2s, 2p).

💡Nitrogen

Nitrogen is used as an example in the video script to demonstrate the process of electron configuration. With seven electrons, nitrogen's electron configuration is worked out as '1s2 2s2 2p3', illustrating the application of the rules for filling orbitals.

💡Helium

Helium serves as a simple example in the video script to show how electrons fill the lowest energy orbitals first. With two electrons, helium's electron configuration is '1s2', demonstrating the principle of filling orbitals with opposite spins.

💡Lithium

Lithium, with three electrons, is used in the video script to explain the progression of electron filling into the next energy level. After filling the 1s orbital, the third electron goes into the 2s orbital, resulting in the electron configuration '1s2 2s1'.

Highlights

Introduction to electron configuration in elements

Explanation of atomic orbitals and their capacity to hold electrons

Differentiation between s, p, d, and f orbitals

Concept of subshells and their composition

Energy levels of subshells and their increase with distance from the nucleus

Three rules for assigning electrons to atomic orbitals

Rule 1: Lowest energy orbitals are filled first

Rule 2: Up to two electrons per orbital with opposite spins

Rule 3: Electrons fill individual orbitals before pairing in same orbital

Demonstration of electron assignment in hydrogen

Electron configuration notation for hydrogen

Explanation of electron spin notation

Electron configuration for helium

Electron configuration for lithium including the 2s orbital

Assignment of nitrogen's seven electrons into orbitals

Electron configuration for nitrogen: 1s2 2s2 2p3

Introduction to exceptions to the electron filling rules

Teaser for the next video with more complex examples

Transcripts

[Music]

hi and welcome back to three science

lessons by the end of this two-part

video you should be able to work out the

electron configuration of elements okay

in the last video we saw that an atomic

orbital is a region around a nucleus

that can hold up to two electrons with

opposite spins we saw that there are

several different types of orbitals and

we call these the s P D and F orbitals

we also saw that a sub shell consists of

all of the orbitals of the same type in

the same shell and I'm showing you the

3d subshell here so in this video we're

going to look at how we assign electrons

to different atomic orbitals the first

key idea you need to understand is that

different sub shells have got different

energies I'm showing you the energies of

some of the sub shells here now I should

point out that at this stage I'm only

looking at a small number of sub shells

we've been looking at the rest in the

next video as you can see as we move

away from the nucleus the energy of the

sub shells increases now in order to

show how electrons fill the orbitals we

need to follow three rules these are

quite straightforward so let's look at

them now firstly orbitals were the

lowest energy are filled first secondly

we can have up to two electrons in the

same orbital but they must have opposite

spins and lastly if we have orbitals

with the same energy then we put

electrons into individual orbitals

before we pair them and that's because

electrons in the same orbital repel

coming up I'm going to show you some

examples of how to put electrons into

orbitals and I'll give you want to try

for yourself

[Music]

okay so let's look at some examples of

how to put electrons into atomic

orbitals we're gonna start with hydrogen

which has got one electron in this case

the lowest energy orbital is the 1s

orbital and shell 1 so here's our

electron and you'll notice that were

using an arrow to show the electron spin

now I should point out that if you're

following the AQA spec then you need to

show an electron using an arrow like

this instead however for the LC aspect

we show electrons using a normal level

which is what I will use now another way

of writing this is to use a shorthand

version showing just the sub shells this

is called the electron configuration in

the case of hydrogen the 1s sub shell

contains one electron so the electron

configuration of hydrogen is one s one

let's look at the element helium helium

has two electrons again the lowest

energy orbital is 1s so our first

electron goes there remember that each

orbital can hold up to two electrons so

that means that our second electron can

also go into the 1s orbital now you'll

notice that we flipped the spin of the

second electron and that's because

electrons in the same orbital must have

opposite spins because helium has two

electrons in the 1s sub shell the

electron configuration of helium will be

1s - okay let's look at lithium now

lithium has three electrons again we can

put the first two electrons into the 1s

orbital like this the 1s orbital is now

full so the third electron now goes into

the second shell the lowest energy

orbital in the second shell is the 2's

orbital so that's where the electron

goes this means that the electron

configuration of lithium is 1s2 2s1

okay I'd like you now to draw the

electrons in their orbitals for the

element nitrogen nitrogen has got seven

electrons I'd also like you to work out

the electron configuration from nitrogen

so pause the video and try this yourself

okay so just like before the first two

electrons go into the 1s sub shell and

here they are the next two electrons go

into the two s subshell we now have

three more electrons to assign now

you'll notice that all of the P orbitals

and the 2p sub-shell have the same

energy remember that if we've got

orbital

with the same energy then we put

electrons into individual orbitals

before we pair them so here are three

electrons and the 2p orbitals the

electron configuration for nitrogen is

1s2 2s2 2p3 as you can see the electron

configuration does not show the

individual orbitals in the 2p sub-shell

and that's because the electron

configuration only shows the sub shells

not the individual orbitals in the next

video we look at more complicated

examples of how orbitals are filled and

we look at two elements that are

exceptions to the rules and explain why

[Music]