Fireworks that contain metallic salts such as sodium, strontium, and barium can generate bright colors. a technician investigates what colors are produced by the metallic salts by performing flame tests. during a flame test, a metallic salt is heated in the flame of a gas burner. each metallic salt emits a characteristic colored light in the flame. 3. state how bright-line spectra viewed through a spectroscope can be used to identify the metal ions in the salts used in the flame tests. 4. explain, in terms of electrons, how a strontium salt emits colored light. 5. explain why the electron configuration of 2-7-1-1 represents a sodium atom in an excited state.

See explanation below

Explanation:

3. Each atom has unique electron energy level when compared to other, when electron relaxes from an excited energy level, it emits energy in the form of electromagnetic waves with energy equals to the difference between energy of ground and excited state. As electromagnetic wave wavelength obeys planck relation

And the energy of each photon in electromangetic wave of specific frequency is

Where h is planck's constant

We can see that the wavelength, which determines color and position of bright line in spectroscope corresponds directly to the energy of electromagnetic wave, and thus, the characteristic energy of atom.

4. From the answer above, you now know that electronic transition can emit electron with specific wavelength. In strontium, emission of colored light occurs by the relaxation of electrons in excited state such that the difference between excited energy level and ground level falls in the energy of visible light spectral range.

5. In Na, ground state configuration is 2-8-1. 2-7-1-1 indicates that one of electron in ground state got excited by external energy to excited state, and thus, indicates that Na atom is in excited state

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

the temperature of the gas, in k, not celsius.