Line Spectrum Observation

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in the flame of a laboratory burner. Thus, flame tests are useful in the identification of metallic ions. Many metallic ions exhibit characteristic colors when vaporized in the burner flame. In this experiment, characteristic colors of several different metallic ions will be observed, and an unidentified ion will be identified by means of its flame test.

Many solid substances---e.g., sodium chloride (NaCl)—may be excited by the thermal energy (heat) of flames. The heat comes from the exothermic combustion reactions occurring in the flame.

Solid sodium chloride consists of sodium ions (Na+) bonded to chloride ions (Cl-). In a Bunsen burner flame, these ions are dissociated, and the separated Na ions combine with free electrons in the flame to form sodium atoms:

Na+ + e- Na

Electrons within the neutral sodium atoms can then be exited to higher energy levels by the heat of the flame:

Na + heat Na (an excited Na atom)

The excited atoms then “relax” back to the ground state and emit light:

Na Na + h(light)

Observation：

lithium -------Red purple

barium -------Yellow

calcium-------brick-red

sodium -------Yellow

potassium------Light blue purple.

V. questions

Question 1:

1 there are certain ions that produce similar color in flame tests. Further identification tests must be used.

2 wavelengths are measured by eye so not quantitative and have difficulty differentiating between similar wavelengths. Would sometimes get wrong phenomenon from our inaccurate vision. The flames also sometimes mix together and mess up our judgment

Question 2:

Barium and sodium ions

Question 3:

The colors observed during the flame test are due to the excitement of the electrons caused by the increased temperature. The electrons "jump" from their ground state to a higher energy level. As they return to ground state they emit visible light. The color of the light is connected to the location of the electrons and the affinity the outer shell electrons have to the atomic nucleus.

Question 4:

a. quanta:

the smallest quantity of radiant energy, equal to Planck’s constant times the frequency of the associated radiation.

b. ground state

quantum mechanical system is its lowest-energy state.

c. excited state

excited state of a system (such as an atom, molecule or nucleus) is any quantum state of the system that has a higher energy than the ground state (that is, more energy than the absolute minimum).

Question5:

A spectrometer is a scientific instrument originally used to split light into an array of separate colors, called a spectrum. The line spectrum will be observed it people use spectroscope to measure the refringence of light across different elements’ tubes.