ATOMIC STRUCTURE

1.1 ATOMIC STRUCTURE
Spectroscopy
Section A

For each of the questions only one of the lettered responses (A-D) is correct.

Select the correct response in each case and mark its code letter by connecting the dots as illustrated on the answer sheet.

1. The flame colour associated with potassium salts is
A Green
B Lilac
C Yellow
D Red

2. Which one of the following statements about the emission spectrum of hydrogen is correct?
A The number and/or position of lines in the spectrum cannot be influenced by external factors.
B The complete spectrum occurs in the visible region.
C The value for the ionisation energy of hydrogen can be determined from the spectrum.
D All the lines in the spectrum correspond to electron transitions from higher energy levels to the ground state.


3. Which one of the following diagrams represents the visible region of the atomic hydrogen spectrum?

A
Energy

B

Energy

C
Energy

D

Energy

4. The atomic spectrum of hydrogen shows
A a continuum in which individual lines are not apparent
B a series of lines which get closer together as the frequency increases
C equally spaced lines not confined to the visible spectrum
D equally spaced lines in groups separated by a continuum in the visible spectrum

5. In the line spectrum of atomic hydrogen in which region of the electromagnetic spectrum will lines not appear?
A infra-red
B ultraviolet
C visible
D X-ray

6. In which one of the following does the flame coloration correspond to the ion?
A Mg2+ yellow
B Sr2+ green
C Ba2+ white
D Ca2+ red


Section B

1. The presence of sodium ions in a sample of sea salt can be determined by flame colours.

(a) What is the flame colour associated with sodium compounds?
[1]

(b) The most prominent line in the visible spectrum of the atomic sodium spectrum has a frequency of 5.085 x 1014 Hz. Calculate the energy, E, of radiation with this frequency.







[2]

2. The Sun largely consists of a mixture of hydrogen and helium, the presence of each being detected by spectroscopy. The line emission spectrum of atomic hydrogen in the ultraviolet region of the electromagnetic spectrum is shown below.



frequency
(a) Explain why this spectrum consists of lines which are converging.







[5]

(b) Explain how the ionisation energy of atomic hydrogen can be calculated from the spectrum.




[2]


3. State the flame coloration for the following chlorides.

Metal chloride
colour
barium chloride

lithium chloride

potassium chloride

[3]