Flame Tests & Bright-Line Spectra

1. Flame Tests & Bright-Line Spectra

2. Flame Tests & Bright-Line Spectra • Visible light is composed of the basic colors red, orange, yellow, green, blue, and violet (R.O.Y.G.B.V.).

3. Flame Tests & Bright-Line Spectra • It was Isaac Newton who proved that visible (“white”) light was composed of the basic colors red, orange, yellow, green, blue, and violet.

4. Flame Tests & Bright-Line Spectra • Light is not just the visible light spectrum (R.O.Y.G.B.V.) but includes radiation such as TV and radio, microwaves, radar, infraredlight, ultraviolet light, X-rays, and gamma rays.

5. visible light gamma rays ultraviolet microwaves X rays infrared TV & radio waves radar frequency (hertz – cycles/s ) 10 24 10 22 10 20 10 18 10 16 10 14 10 12 10 10 10 8 10 6 10 4 High Energy Low Energy 10 –16 10 –14 10 –12 10 –10 10 –8 10 –6 10 –4 10 –2 10 0 10 2 10 4 wavelength (meters) violet blue green yellow orange red 750 nm 400 nm 450 nm 500 nm 550 nm 600 nm 650 nm 700 nm wavelength (nm) Flame Tests & Bright-Line Spectra • Light is not just the visible light spectrum (R.O.Y.G.B.V.) but includes radiation such as TV and radio, microwaves, radar, infraredlight, ultraviolet light, X-rays, and gamma rays.

6. visible light gamma rays ultraviolet microwaves X rays infrared TV & radio waves radar frequency (hertz – cycles/s ) 10 24 10 22 10 20 10 18 10 16 10 14 10 12 10 10 10 8 10 6 10 4 High Energy Low Energy 10 –16 10 –14 10 –12 10 –10 10 –8 10 –6 10 –4 10 –2 10 0 10 2 10 4 wavelength (meters) violet blue green yellow orange red 750 nm 400 nm 450 nm 500 nm 550 nm 600 nm 650 nm 700 nm wavelength (nm) Flame Tests & Bright-Line Spectra • All light travels in waves of tiny individual packages of energy calledphotons. • Every photon has a specific frequency, wavelength, and energy.

7. visible light gamma rays ultraviolet microwaves X rays infrared TV & radio waves radar frequency (hertz – cycles/s ) 10 24 10 22 10 20 10 18 10 16 10 14 10 12 10 10 10 8 10 6 10 4 10 –16 10 –14 10 –12 10 –10 10 –8 10 –6 10 –4 10 –2 10 0 10 2 10 4 wavelength (meters) violet blue green yellow orange red 750 nm 400 nm 450 nm 500 nm 550 nm 600 nm 650 nm 700 nm wavelength (nm) Flame Tests & Bright-Line Spectra • Gamma rays and x-raysare high energy lightwhile TVand radio wavesare low energy light. • Violet lightis high energy visible light whilered lightis low energy visible light. High Energy Low Energy High Energy Low Energy

8. Flame Tests & Bright-Line Spectra • When ions of certain elements are heated in a flame, each element gives off a specific color called theflame test color. Barium Calcium Copper Lithium Potassium Sodium Strontium

9. Flame Tests & Bright-Line Spectra • Road flares are a practical use of flame test colors.

10. Flame Tests & Bright-Line Spectra • Fireworks are a spectacular example of flame test colors.

11. Flame Tests & Bright-Line Spectra – give off light! • When materials are heated, they often begin toglow – • Incandescent light bulbs are a good example of this.

12. Flame Tests & Bright-Line Spectra • The light from a glowing material can be studied by observing it with a spectroscope. • A spectroscope is an instrument that will separate light into its various wavelengths – thus into its various colors.

13. Flame Tests & Bright-Line Spectra • After the spectroscope was invented in 1859, scientist began to use it to study glowing objects. • This is what scientists saw when looking at sunlight through a spectroscope:

14. sodium hydrogen 400 nm 400 nm 500 nm 500 nm 600 nm 600 nm 700 nm 700 nm Flame Tests & Bright-Line Spectra • This is what scientists saw in the spectro-scope when looking at glowing hydrogen gas: • This is what scientists saw in the spectro-scope when looking at glowing sodium vapor:

15. mercury lithium 400 nm 400 nm 500 nm 500 nm 600 nm 600 nm 700 nm 700 nm Flame Tests & Bright-Line Spectra • This is what scientists saw in the spectro-scope whenlookingat glowingmercury vapor: • This is what scientists saw in the spectro-scope when looking at glowing lithium vapor:

16. helium cadmium 400 nm 400 nm 500 nm 500 nm 600 nm 600 nm 700 nm 700 nm Flame Tests & Bright-Line Spectra • This is what scientists saw in the spectro-scope whenlookingat glowing helium gas: • This is what scientists saw in the spectro-scopewhenlookingatglowingcadmiumvapor:

17. hydrogen 400 nm 500 nm 600 nm 700 nm Flame Tests & Bright-Line Spectra • Each element has its own unique pattern of colored lines called the bright-line spectrum. • An element’s bright-line spectrum is like a fingerprint... ... In that the pattern of lines at specific wavelengths can be used to identify the presence of an element.

18. Flame Tests & Bright-Line Spectra • When looking directly at the sun, scientists discovered a series of lines that did not correspond to any of the known elements! • A new element had been discovered! –helium

19. Flame Tests & Bright-Line Spectra • Scientists called this new elementheliumbecause the Greek word for sun washelios. • At first, its was believed that helium was only found in the sun.

20. Flame Tests & Bright-Line Spectra • Helium was discovered on earth more than 20 years after it had been discovered in the sun! • Helium is much less dense than air and so it is used in party balloons and in blimps.

21. Flame Tests & Bright-Line Spectra • Every known element has its own unique bright-line spectrum. • For years it puzzled scientists why this was so. • Since each element is composed of unique atoms... ... It must be the atoms! • How do the atoms of each element produce the element’s unique bright-line spectrum?