For Lithium ions (Li+1) the color was observed is red, according to the electrom

Question

For Lithium ions (Li+1) the color was observed is red, according to the electromagnetic radiation figure, the red color has (665 nm wavelength): 1. Convert from nm to meter : 2. Use the energy equation to calculate E: Questions: 1. Show one sample of calculation. 2. Based on the energy value, place the following elements of the scale below from lowest energy to highest energy: Ca, K, Sr, Cu, Na 3. How can a flame test be used to identify an unknown element?
For Lithium ions (Li+1) the color was observed is red, according to the electromagnetic radiation figure, the red color has (665 nm wavelength): 1. Convert from nm to meter : 2. Use the energy equation to calculate E: Questions: 1. Show one sample of calculation. 2. Based on the energy value, place the following elements of the scale below from lowest energy to highest energy: Ca, K, Sr, Cu, Na 3. How can a flame test be used to identify an unknown element?
For Lithium ions (Li+1) the color was observed is red, according to the electromagnetic radiation figure, the red color has (665 nm wavelength): 1. Convert from nm to meter : 2. Use the energy equation to calculate E: Questions: 1. Show one sample of calculation. 2. Based on the energy value, place the following elements of the scale below from lowest energy to highest energy: Ca, K, Sr, Cu, Na 3. How can a flame test be used to identify an unknown element?

Explanation / Answer

1.

= 665 nm

= 665 x 10-9 m

2.

E= hc/

h = 6.625 x 10-34 Js

c = 3 x 108 m/s

= 665 x 10-9 m

E= hc/ = (6.625 x 10-34 Js) x (3 x 108 m/s) /  665 x 10-9 m

E=0.02988x 10-17 J = 2.998x10-19 J

E = 2.998x10-19 J

2. Lowest energy to highest energy:

K, Na, Sr, Ca, Cu

3. How can a flame test be used to identify an unknown element?

The ionisation energy of the alkali and alkali earth metals are low. So using the flame of the burner, the valence electrons are excited to higher energy. When the electrons comes back to its orignal position the difference in the energy between the excited state to the ground state is given a light which falls in the visible range of the electromagnetic spectrum. The color of these elements are difference and hence these colors can be used to identify the presence of the elements in the sample. Sodium gives yellow color, Calcium gives red on the flame.

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