Ionisation - Spectroscopy

Question 0

What does a complete spectrum consist of and what is it called?

Answer 0

It is composed of all visible wavelengths of light and is called a continuous spectrum.

Question 1

How is a complete light spectrum formed?

Answer 1

When light is shone through a slit and the resulting beam is shone through a prism onto a screen a rainbow of separated colours is seen.

Question 2

Name the types of E.M radiation from highest energy to lowest

Answer 2

Gamma rays

X rays

ultraviolet

Visible (blue)

Visible (yellow)

Visible (red)

Infrared

Microwaves

Radio waves

Question 3

What is monochromatic light?

Answer 3

Light consisting of only one wavelength.

Question 4

How is frequency related to the velocity and wavelength of light.

Answer 4

F=V/wavelength

Question 5

How is frequency related to the energy of the radiation?

Answer 5

As the frequency increases so does the energy of the E.M radiation and is expressed as E=hF where “h” is Planck’s constant

Question 6

How is an emission spectrum created?

Answer 6

A gas source is excited (by subjecting it to an electric current at a low pressure) until it begins to emit light which then passes through a prism and onto a screen.

Question 7

Give an example where subjecting a gas to a potential difference to emit light is used?

Answer 7

Advertising signs and sodium vapour street lamps.

Question 8

How is an absorption spectrum formed.

Answer 8

By shining white light through a gas and projecting it through a prism onto a screen.

Question 10

What is the appearance of an emission spectrum?

Answer 10

This consists of a series of bright, coloured, discrete lines on a black background.

Question 11

What is the appearance of an absorption spectrum?

Answer 11

A series of discrete black lines upon a bright, coloured background.

Question 12

How are absorption and emission spectra related?

Answer 12

The bright lines on the emission spectrum correspond exactly to the position of the dark lines on an absorption spectrum for the same light source.

Question 13

What type of spectra are emission and absorption spectra?

Answer 13

Line spectra.

Question 14

What does the hydrogen emission spectrum consist of?

Answer 14

A number of separate sets of lines.

Question 15

Describe the trend seen in each set of lines in the hydrogen spectrum.

Answer 15

The intervals between the between the lines gets smaller as the frequency increases until they coalesce.

Question 16

What are the three series’s in the hydrogen spectrum and in what regions of the spectrum do they reside?

Answer 16

Paschen & Brackett - infrared.
Balmier - visible.
Lyman - ultraviolet.

Question 17

What did max Planck state His quantum theory and what is the implication of this theory?

Answer 17

That energy couldn’t be held by particles or atoms in any arbitrary amount but only in specified amounts called quanta.

A particle cannot change its energy continuously but only by a series of steps.

Question 18

How did Niels Bhor apply max plank’s quantum theory to the hydrogen spectrum?

Answer 18

By suggesting that electrons can only exist in certain defined energy states and that they can only move between these states by absorbing or emitting quanta of energy in the form of radiation. The lower energy states correspond to inner orbits and the higher energy states the outer.

Question 19

How are lines in the emission and absorption spectrum caused?

Answer 19

Absorption - an electron is excited by absorbing a quantum of energy and goes from a lower energy level to a higher one.

Emission - a line in the emission spectrum results from an excited electron in a higher energy level falling to a lower one, releasing a quantum of energy which takes the form of light of a certain frequency.

Question 20

How are energy levels labelled?

Answer 20

The energy level closest to the nucleus is called the n=1 energy level and an electron in this level is in its ground state. The next orbit has the quantum number 2 (n=2) etc.

Question 21

When is an atom ionised?

Answer 21

When an electron moves in the layman series from the n=1 energy level to the point where they coalesce n=infinity (the convergence limit) it has escaped the pull of the nucleus and has become an ion.

Question 22

How can the ionisation energy be calculated from an emission spectrum?

Answer 22

The frequency of the convergence limit in the in the lyman series can be used to calculate the ionisation energy using E=hF where “h” is Planck’s constant and “f” is the frequency of convergence.

Question 23

Explain the origins of the first four lines in the balmier series.

Answer 23

1st: N=3 falls to n=2
2nd: N=4 falls to n=2
3rd: N=5 falls to n=2
4th: N=6 falls to n=2

Question 24

What does the hydrogen emission spectrum consist of?

Answer 24

A number of separate sets of lines.

Question 25

Describe the trend seen in each set of lines in the hydrogen spectrum.

Answer 25

The intervals between the between the lines gets smaller as the frequency increases until they coalesce.

Question 26

What are the three series’s in the hydrogen spectrum and in what regions of the spectrum do they reside?

Answer 26

Paschen & Brackett - infrared.
Balmier - visible.
Lyman - ultraviolet.

Question 27

What did max Planck state His quantum theory and what is the implication of this theory?

Answer 27

That energy couldn’t be held by particles or atoms in any arbitrary amount but only in specified amounts called quanta.

A particle cannot change its energy continuously but only by a series of steps.

Question 28

How did Niels Bhor apply max plank’s quantum theory to the hydrogen spectrum?

Answer 28

By suggesting that electrons can only exist in certain defined energy states and that they can only move between these states by absorbing or emitting quanta of energy in the form of radiation. The lower energy states correspond to inner orbits and the higher energy states the outer.

Question 29

How are lines in the emission and absorption spectrum caused?

Answer 29

Absorption - an electron is excited by absorbing a quantum of energy and goes from a lower energy level to a higher one.

Emission - a line in the emission spectrum results from an excited electron in a higher energy level falling to a lower one, releasing a quantum of energy which takes the form of light of a certain frequency.

Question 30

How are energy levels labelled?

Answer 30

The energy level closest to the nucleus is called the n=1 energy level and an electron in this level is in its ground state. The next orbit has the quantum number 2 (n=2) etc.

Question 31

When is an atom ionised?

Answer 31

When an electron moves in the layman series from the n=1 energy level to the point where they coalesce n=infinity (the convergence limit) it has escaped the pull of the nucleus and has become an ion.

Question 32

How can the ionisation energy be calculated from an emission spectrum?

Answer 32

The frequency of the convergence limit in the in the lyman series can be used to calculate the ionisation energy using E=hF where “h” is Planck’s constant and “f” is the frequency of convergence.

Question 33

Explain the origins of the first four lines in the balmier series.

Answer 33

1st: N=3 falls to n=2
2nd: N=4 falls to n=2
3rd: N=5 falls to n=2
4th: N=6 falls to n=2