Flame Tests & Bright-Line Spectra

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.).

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.

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, infrared light, ultraviolet light, X-rays, and gamma rays.

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, infrared light, ultraviolet light, X-rays, and gamma rays.

10 –16 10 –14 10 –12 10 –10 10 –8 10 –6 10 –4 10 –2 10 0 10 2 10 4

wavelength (meters)

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

gamma rays

X rays

ultraviolet

visible light

infraredradar

microwavesTV & radio waves

400 nm 450 nm 500 nm 550 nm 600 nm 650 nm 700 nm 750 nm

redviolet blue green yellow orange

wavelength (nm)

Low EnergyHigh Energy

Flame Tests & Bright-Line Spectra All light travels in waves of tiny individual

packages of energy called photons.

Every photon has a specific frequency, wavelength, and 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)

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

gamma rays

X rays

ultraviolet

visible light

infraredradar

microwavesTV & radio waves

400 nm 450 nm 500 nm 550 nm 600 nm 650 nm 700 nm 750 nm

redviolet blue green yellow orange

wavelength (nm)

Low EnergyHigh Energy

Flame Tests & Bright-Line Spectra Gamma rays and x-rays are high energy light

while TV and radio waves are low energy light.

Violet light is high energy visible light while red light is low energy visible light.

Low EnergyHigh 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)

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

gamma rays

X rays

ultraviolet

visible light

infraredradar

microwavesTV & radio waves

400 nm 450 nm 500 nm 550 nm 600 nm 650 nm 700 nm 750 nm

redviolet blue green yellow orange

wavelength (nm)High Energy Low Energy

Flame Tests & Bright-Line Spectra When ions of certain elements are heated

in a flame, each element gives off a specific color called the flame test color.

Barium

PotassiumLithiumCopper

Calcium

StrontiumSodium

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

colors.

Flame Tests & Bright-Line Spectra Fireworks are a spectacular example of flame

test colors.

Flame Tests & Bright-Line Spectra When materials are heated, they often begin

to glow – Incandescent light bulbs are a good example

of this.

– give off light!

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.

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:

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:

400 nm 500 nm 600 nm 700 nm

sodium

400 nm 500 nm 600 nm 700 nm

hydrogen

Flame Tests & Bright-Line Spectra This is what scientists saw in the spectro-

scope when looking at glowing mercury vapor:

This is what scientists saw in the spectro-scope when looking at glowing lithium vapor:

400 nm 500 nm 600 nm 700 nm

mercury

400 nm 500 nm 600 nm 700 nm

lithium

Flame Tests & Bright-Line Spectra This is what scientists saw in the spectro-

scope when looking at glowing helium gas:

This is what scientists saw in the spectro-scope when looking at glowing cadmium vapor:

400 nm 500 nm 600 nm 700 nm

helium

400 nm 500 nm 600 nm 700 nm

cadmium

400 nm 500 nm 600 nm 700 nm

hydrogen

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.

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

Flame Tests & Bright-Line Spectra Scientists called this new element helium

because the Greek word for sun was helios.

At first, its was believed that helium was only found in the sun.

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.

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?