Ocean County College Department of Chemistry Identification of Metallic Ions Purpose: The purpose of this lab exercise was to perform and observe the flame tests of some alkali and alkaline earth metal ions. When electrons in metallic ions are grounded, their configuration is stable. In other words, the loosely bound electrons in the valence shell of the atom are satisfied at their “low” energy state. They do not require to be balanced by emitting any type of radiation or receiving any additional electrons.
However, these stable, grounded electrons in the metallic ions become excited to higher energy levels due to the presence of heat, thus losing their stability. They absorb heat energy, but counteract by releasing the absorbed energy to become grounded once again. This released energy comes in the form of electromagnetic energy. Some of the released heat energy is in the visible light region. The metallic ions being heated disperse unique colors which are characteristic ranging from a lower energy (red) to a high energy (violet) and some colors in between.
We can learn much about the element we’re working with by simply observing the color flame that is produced. Flame tests are a common confirmation test to identify specific elements. Procedure: I began the lab by preparing a safe work area and the required metallic ions. The ions used in this lab were as follows: Barium Nitrate, Calcium Nitrate, Cupric Nitrate, Lithium Nitrate, Potassium Nitrate, Sodium Nitrate, Strontium Nitrate, and an unknown solution. I placed 0. 5 mL of sodium nitrate into a well on the 24-well plate, recording its location.
I placed 0. 5 mL of the other 7 solutions in 7 other wells on the plate, recording their locations as well. I soaked the tip of a cotton swab into the solution of sodium nitrate and passed the soaked end through the flame several times until I noticed a color change. I recorded all observations in the Data Table chart below. I repeated these steps for the other 7 solutions. Data Table: Observations Column1| Column2| Metallic Ion| Flame Color| Sodium Nitrate| Orange/yellow| Strontium Nitrate| Deep Crimson Red|
Potassium Nitrate| Violet| Barium Nitrate| Green/Yellow| Lithium Nitrate| Deep Crimson Red| Calcium Nitrate| Orange| Cupric Nitrate| Blue/Green| Unknown (Lithium)| Deep Crimson Red| Conclusion: The flame test was a success and satisfied my learning objective. Since every metal gives the flame a different color, I was able to identify most of the given elements with a slight room for error. The unknown solution gave off a deep crimson red glow which could have been either strontium nitrate or lithium nitrate.
I went with the latter after doing the test several times, comparing the glows. Dimming the light in the room helped tremendously to get a better idea of the true color of each flame. Although this method isn’t perfect to identify more unknown ions due to the slight variations of colors, it does the job. The low energy metallic ions include were Strontium and Lithium. The moderate energy ions were Sodium, Barium, and Calcium. The higher energy ions were Copper and Potassium.