3.5 Energy Levels and Spectra

Question 1

What is a rainbow

Answer 1

A natural display of the colours of the spectrum of sunlight

Raindrops split sunlight into a continuous spectrum of colours

Question 2

What is the difference between using a tube of glowing gas as the light source instead of a filament lamp when looking at colour spectrums

Answer 2

We see a spectrum of discrete lines of different colours rather than a continuous spectrum

Question 3

The wavelengths of the lines of a line spectrum of an element are characteristic of…

Answer 3

…the atoms of that element

Question 4

How can we identify the element that produced the light from a line spectrum

Answer 4

By measuring the wavelengths

No other element produces the same pattern of light wavelengths

Question 5

Why does every element produce a different pattern of light wavelengths

Answer 5

Because the energy levels of each type of atom are unique to that atom so photons emitted are characteristic of the atom.

Question 6

What is each line in a line spectrum due to

Answer 6

Light of a certain colour and therefore a certain wavelength

Question 7

The photons that produce each line all have the ______ energy, which is ______ from the energy of the photons that produce any other line.

Answer 7

Same

Different

Question 8

Each photon is emitted when an atom de-excites due to…

Answer 8

… one of its electrons moving to an inner shell

Question 9

If the electron moves from energy level E1 to a lower energy level E2, the energy of the emitted photon hf =

Answer 9

E1 - E2

Question 10

What is the simplest type of atom

Answer 10

The hydrogen atom

One proton as its nucleus and one electron

Question 11

General formula for the energy levels of the hydrogen atom relative to the ionisation level

Answer 11

E = - 13.6eV / n^2

Where n=1 for the ground state, n=2 for the next excited state etc.

Question 12

When a hydrogen atom de-excites from energy level n1 to a lower energy level n2, the energy of the emitted photon is given by…

Answer 12

E = (1/n2^2 - 1/n1^2) * 13.6 eV

Question 13

What does each energy level correspond to

Answer 13

The electron in a particular shell.

Question 14

How was the energy level formula for hydrogen first deduced?

Answer 14

From the measurements of the wavelengths of the lines

Question 15

Why are measurements of the wavelength of light important in branches of science such as astronomy and forensic science

Answer 15

They enable us to identify the chemical elements in the light source.

Question 16

What was helium discovered from

Answer 16

The spectrum of sunlight
Pattern of lines in spectrum was observed at wavelengths that had never been observed from any known gas and were therefore due to presence of previously unknown element in the Sun.

Question 17

How is helium produced

Answer 17

As a result of the nuclear fusion of hydrogen nuclei in the Sun
Named after Greek word ‘Helios’ for Sun

Question 18

How is helium produced in the earth

Answer 18

As alpha particles from the radioactive decay of elements such as uranium.
Can be collected at oil wells and stored for use in fusion reactors, helium-neon lasers and for very low temperature devices.

Question 19

What happens to helium in liquid state below a temperature of 2.17K

Answer 19

Becomes a superfluid

Question 20

What is a superfluid

Answer 20

A fluid with no resistance to flow, which escapes from an open container by creeping - as a thin film - up and over the sides of the container