S1.3.1 - The hydrogen emission spectrum

Summary

This educational video script delves into the concept of the hydrogen emission spectrum, illustrating the behavior of light when passed through a prism versus a hydrogen gas lamp. It explains how hydrogen atoms, when excited, emit light at specific frequencies, creating a line spectrum. The script uses the Bohr model to describe electron transitions between energy levels, correlating these transitions with the observed spectral lines. It concludes by emphasizing that while some emissions are visible, others fall into the ultraviolet or infrared spectrum, invisible to the human eye.

Takeaways

• 🌈 Light passing through a prism creates a continuous spectrum, showing all visible frequencies of light.
• 💡 A hydrogen gas lamp, when excited, emits a line spectrum with specific frequencies, unlike the continuous spectrum of a light bulb.
• 🔬 The hydrogen emission spectrum is produced by excited hydrogen atoms releasing specific frequencies of light as their electrons drop to lower energy levels.
• 📊 The line spectrum shows discrete lines corresponding to specific energy transitions within the hydrogen atom.
• ⚛️ The hydrogen atom model with energy levels helps explain the observed lines in the emission spectrum.
• ⬆️ Electrons in a hydrogen atom can absorb specific frequencies of energy to jump to higher energy levels (excited states).
• ⬇️ When electrons drop back to lower energy levels, they release the exact same amount of energy they absorbed.
• 🔴 The red line in the hydrogen emission spectrum corresponds to the transition from the third to the second energy level.
• 🟢 The green, blue, and violet lines represent transitions from higher energy levels (fourth, fifth, sixth) to the second energy level.
• 🌟 The convergence of lines in the hydrogen emission spectrum suggests that energy levels in an atom get closer as they increase.

Q & A

What happens when white light passes through a prism?

When white light passes through a prism, it is refracted and split into a spectrum of colors, creating a continuous rainbow-colored spectrum that represents all the frequencies of visible light.

What is a continuous spectrum?

A continuous spectrum is one that shows all frequencies of light within a certain range, such as the visible spectrum, without any gaps.

How does the light emitted from a hydrogen gas lamp differ from that of a light bulb?

The light emitted from a hydrogen gas lamp is a line spectrum, which shows only specific frequencies of light, as opposed to the continuous spectrum produced by a light bulb.

Why is the word 'frequency' important when describing the hydrogen emission spectrum?

Using the term 'frequency' instead of 'color' is important for accuracy in scientific terminology, especially in exams, as it refers to the specific energy of the light, not just its appearance.

What is the ground state of a hydrogen atom?

The ground state of a hydrogen atom is the most stable state where its single electron is in the lowest energy level.

How does an electron in a hydrogen atom absorb energy?

An electron in a hydrogen atom absorbs a specific frequency of energy, which allows it to jump to a higher energy level, entering an excited state.

What happens when an electron in an excited state drops back to a lower energy level?

When an electron drops back to a lower energy level, it releases the exact same amount of energy it absorbed, which can be observed as light of a specific frequency.

How are the lines in the hydrogen emission spectrum related to the energy levels of the atom?

Each line in the hydrogen emission spectrum corresponds to an electron dropping from a higher energy level to a lower one, often to the second energy level, and the energy released during these drops corresponds to visible light frequencies.

What does the convergence of lines in the hydrogen emission spectrum suggest about the energy levels of the atom?

The convergence of lines in the hydrogen emission spectrum suggests that the energy levels of the atom get closer together as they increase, indicating a structure to the atom's energy levels.

Why are some emissions from the hydrogen atom not visible to the human eye?

Emissions from the hydrogen atom that involve electrons dropping to the first or third energy levels are not visible because they correspond to ultraviolet or infrared light, which are outside the range of human vision.

How can the energy level diagram simplify the representation of transitions in the hydrogen atom?

An energy level diagram simplifies the representation of transitions by showing the energy levels as horizontal lines, with the electron's jumps between levels indicated by arrows, making it easier to visualize the energy changes.

Outlines

00:00

🌈 Understanding the Hydrogen Emission Spectrum

This paragraph introduces the concept of the hydrogen emission spectrum by comparing it with the continuous spectrum of white light. The continuous spectrum is demonstrated using a prism to split white light into its constituent colors, representing different frequencies of light. In contrast, when a hydrogen gas lamp is used, the emitted light through the prism shows a line spectrum, indicating specific frequencies. This line spectrum is unique to hydrogen and is produced when hydrogen atoms are excited by energy, causing their electrons to jump to higher energy levels and then release energy as they return to lower levels. The paragraph also explains the process of electron excitation and the importance of energy level transitions in the context of the hydrogen atom's structure.

05:01

🔬 Energy Level Transitions and the Hydrogen Spectrum

The second paragraph delves into the specific energy level transitions that correspond to the lines seen in the hydrogen emission spectrum. It describes how the electron in a hydrogen atom, when excited, can jump to various higher energy levels and then drop back down, releasing energy in the form of light. The paragraph identifies the colors of the spectrum (red, green, blue, violet) with the energy level transitions, suggesting that each color represents a drop from a higher energy level to the second energy level. The explanation also touches on how the energy levels converge at higher states, which is reflected in the spectrum's lines getting closer together as energy increases. The paragraph concludes by summarizing that the hydrogen emission spectrum is a result of electrons dropping to the second energy level, with other possible transitions occurring in the ultraviolet and infrared spectra, which are not visible to the human eye.

Keywords

💡Hydrogen Emission Spectrum

The hydrogen emission spectrum refers to the series of bright lines seen when light emitted by hydrogen gas is passed through a prism. In the video, this spectrum is used to illustrate the quantized nature of energy levels within a hydrogen atom. Each line in the spectrum corresponds to a specific energy transition within the atom, demonstrating that electrons can only occupy certain discrete energy levels.

💡Prism

A prism is an optical device made of glass or other transparent materials with flat, polished surfaces that refract light. In the video, a prism is used to disperse white light from a light bulb into its constituent colors, creating a continuous spectrum. This process is essential for demonstrating the difference between a continuous spectrum and the discrete lines of the hydrogen emission spectrum.

💡Continuous Spectrum

A continuous spectrum is a spectrum that includes all possible frequencies of light, creating a smooth, uninterrupted band of colors. The video describes how passing white light through a prism results in a continuous spectrum, which contrasts with the discrete lines of the hydrogen emission spectrum. This concept is crucial for understanding the nature of light and the energy transitions within atoms.

💡Energy Levels

Energy levels are specific, quantized states of energy that electrons in atoms can occupy. The video explains that when energy is passed through a hydrogen atom, electrons can absorb energy and jump to higher energy levels, or drop to lower ones, emitting light in the process. The concept of energy levels is central to understanding atomic structure and the behavior of electrons.

💡Ground State

The ground state is the lowest energy state of an atom or molecule, where the electron is in its lowest possible energy level. In the video, the hydrogen atom's ground state is represented by the electron in the first energy level. This state is the most stable, and understanding it is key to explaining how atoms absorb and emit energy.

💡Excited State

An excited state is a higher energy state that an electron can reach when it absorbs energy. The video describes how electrons in hydrogen atoms can be excited by energy from electricity or heat, causing them to move to higher energy levels. The concept of excited states is essential for explaining the emission of light and the formation of the hydrogen emission spectrum.

💡Frequency

Frequency refers to the number of occurrences of a repeating event per unit of time, and in the context of light, it is related to the color or energy of the light. The video emphasizes the importance of using 'frequency' rather than 'color' when discussing the hydrogen emission spectrum, as it is a more precise term for describing the energy transitions that produce the spectrum's lines.

💡Line Spectrum

A line spectrum is a series of discrete lines that represent specific frequencies of light emitted or absorbed by an atom. In the video, the hydrogen emission spectrum is described as a line spectrum, showing only specific frequencies of light. This is in contrast to a continuous spectrum and is used to demonstrate that atoms can only emit or absorb light at certain frequencies corresponding to their energy level differences.

💡Energy Transition

An energy transition is the process by which an electron moves between different energy levels within an atom, either by absorbing or emitting energy. The video explains that when electrons in hydrogen atoms transition from higher energy levels to lower ones, they emit light at specific frequencies, resulting in the lines seen in the hydrogen emission spectrum.

💡Bohr Model

The Bohr model is a theoretical model of the atom that explains the hydrogen emission spectrum by proposing that electrons orbit the nucleus in specific, quantized energy levels. The video uses the Bohr model to explain how the emission spectrum relates to the structure of the hydrogen atom, suggesting that the energy levels converge at higher energies, which is reflected in the spectrum's converging lines.

💡UV and Infrared Spectrum

The UV (ultraviolet) and infrared spectrum are parts of the electromagnetic spectrum that are not visible to the human eye. The video mentions that emissions from energy transitions to the first energy level would be in the UV spectrum, while transitions to higher energy levels would be in the infrared. This highlights that the visible hydrogen emission spectrum is just a part of the broader spectrum of energy transitions possible in atoms.

Highlights

Light passing through a prism creates a continuous spectrum of visible light.

Hydrogen gas lamp emits a line spectrum with specific frequencies of light.

Line spectrum shows only specific frequencies, unlike the continuous spectrum.

Hydrogen emission spectrum is produced when hydrogen gas is excited by energy.

Hydrogen atom model with electron in ground state and energy levels represented.

Electrons absorb specific frequency of energy to jump to higher energy levels.

Electrons release the same amount of energy when dropping back to lower levels.

Multiple possible electron transitions in hydrogen atom due to various energy levels.

Each line in the hydrogen emission spectrum corresponds to an electron transition.

Red line in spectrum represents transition from third to second energy level.

Green line corresponds to transition from fourth to second energy level.

Blue line is due to transition from fifth to second energy level.

Violet line indicates transition from sixth to second energy level.

Energy levels in the atom converge as they move outward.

Emissions from higher energy levels to the second level are visible light.

Emissions to the first energy level would be in the UV spectrum, invisible to the eye.

Emissions to the third energy level would be in the infrared spectrum.

Emission spectra are produced by excited electrons dropping to lower levels.

Hydrogen emission spectrum suggests discrete energy levels in atoms.

Lines in the visible spectrum are due to drops to the second energy level.

Transcripts

before we try to explain the hydrogen

emission spectrum it's useful to think a

little bit about

light so let's take a light bulb

and let's pass that light through a

prism

and as you can see in this diagram as my

white light

passes through the prism the different

wavelengths or

colours or frequencies of light are

refracted

and end up being split into a nice

rainbow coloured spectrum

and we're focusing here just on the

visible part of the spectrum because

that's the bit that we can see with our

eyes

now this spectrum is considered a

continuous spectrum

because it shows all of the frequencies

of light

in that visible part of the spectrum

let's now try the same thing but instead

of a light bulb we're going to use a

hydrogen gas lamp

so in my gas lamp i've got lots of

hydrogen atoms floating around

and what i'm going to do is pass lots of

energy

through my gas lamp using electricity or

heat

and again we're going to pass the light

that's emitted from this gas lamp

through a prism and it's going to look

something like this

so in this diagram you can see that the

emitted light only contains

very specific frequencies of light which

is why we end up seeing a

line spectrum with just single lines of

color

and not a continuous spectrum so a line

spectrum

is a spectrum that shows only specific

frequencies of light

and it's important to use the word

frequency and not color

otherwise you won't get the mark in an

exam

the spectrum we can see here is called

the hydrogen emission spectrum

because it is the line spectrum produced

when

a gas lamp of hydrogen is excited by

lots of energy

before we try and explain how those

lines relate to the structure of an atom

let's first think about what actually

happens in a hydrogen atom

when i pass lots of energy through so

here is a

simple ball model of a hydrogen atom

where the nucleus would be a very small

dot somewhere right in the middle

and the rings are representing different

energy levels

we know that hydrogen has one electron

so let's put that in the lowest

energy level and this would be known as

the ground state

or the most stable state of my atom

as i pass lots of energy through my

hydrogen atom

an electron can absorb a very specific

frequency of energy

and jump up to a higher energy level

where the electron is now in an excited

state

it's important to note for the electron

to jump up to that next energy level

it has to absorb exactly the energy

difference

from the first energy level to the

second energy level

which is why in this process only a

specific frequency of energy is absorbed

conversely when that electron drops back

down to the first energy level

according to the conservation of energy

it must

release that exact same amount of energy

to do so

now of course because there are lots of

different energy levels my electron

could jump

up to the second energy level or the

third or fourth or fifth and so on

and also can drop back down to any of

the lower levels

which means there's a number of possible

transitions that can occur

let's now see if we can identify the

exact transitions that are occurring

to produce our hydrogen emission

spectrum that we saw earlier

so here's the emission spectrum we saw

from our hydrogen gas lamp earlier

it's worth noting on here that the low

energy end of the visible light spectrum

is at the red side and the high energy

end

is at the violet side let's now draw the

boar model of a hydrogen atom as we saw

before

and you can see my blue dot representing

an electron in the ground state

and you'll often see the energy levels

labeled as

n equals 1 for the first energy level

n equals 2 for the second energy level

and so on

now instead of having to draw hundreds

of circles in an exam

we can actually simplify this diagram

into an energy level diagram

which is effectively taking a little

cross section like this

and representing it as the following

so what ball suggested is that each of

the frequencies or colors of light that

i can see on my line spectrum

represent an electron dropping from a

higher energy level

down to the second energy level

now given that there are four lines on

my hydrogen emission spectrum

let's start with the red line which is

the lowest

energy or lowest frequency

transition so i'm looking for the

smallest gap

or the smallest drop down to the second

energy level

and that's going to be a transition from

the third energy level

dropping down to the second if i go

back to my hydrogen emission spectrum

the next highest energy

emission is the green line so that's

going to represent the next

biggest drop to the second energy level

which would be from the fourth energy

level

the next highest energy line on my

emission spectrum is the blue one

which must be representing a drop from

the fifth energy level to the second

and finally the violet line must be

representing a drop from the sixth

energy level

down to the second the brilliant thing

about

the ball model of the atom is that he

looked at the emission spectrum and

noticed that as i move from low energy

to high energy

emissions the lines begin to converge or

get closer together

and this suggested that as i move out in

my energy levels in the atom

the energy levels must also get closer

together and converge

so at some point when the energy levels

are effectively

in the same place we reach the edge of

our atom

the key point in our explanation of the

hydrogen emission spectrum

is that these lines are all representing

emissions or drops

from higher energy levels down to the

second energy level

because it so happens that the energy

released in those drops

corresponds to light on the visible part

of the spectrum

that we can see with our eyes however of

course there are many other

emissions that could occur for example

emissions caused by electrons dropping

back down to the first energy level

now because the amount of energy

released when electrons drop to the

first energy level is much greater

these emissions would actually be seen

on the uv part of the spectrum

that we can't see with our eyes

and conversely if i think about

electrons dropping down to the third

energy level

the amount of energy being released here

is very low

so we would expect to see it on the

infrared part of the spectrum

which again we can't see with our eyes

and just like with my hydrogen emission

spectrum

on the visible part we would expect

these lines to converge as well

indicating that energy levels in an atom

converge as we move out

let's now try to summarize the key

points from this video

firstly emission spectra are produced

when

energy or photons are omitted by excited

electrons

dropping to lower energy levels

secondly the hydrogen emissions spectrum

suggests that electrons are found in

discrete energy levels that converge

at higher energies

and thirdly lines in the visible part of

the spectrum

are caused by electrons dropping to the

n equals two or

second energy level

any drops to the first energy level

would be seen in the uv

part of the spectrum

and drops to the third energy level

would be seen in the infrared part of

the spectrum

hopefully this video is of some help