HYDROGEN ATOM AND SPECTROSCOPY.

Energy Levels for the Hydrogen atom.

Energy levels for the Hydrogen Atom

• Results from solving the Schrödinger equation for the hydrogen atom

• Z is the atomic number

• me is the mass of an electron

• e is the charge of an electron or proton

• h is Planks constant

• r is atomic radius

• e0 is the permittivity of free

space

• Agrees with experimental results

Equation for energy level of a hydrogen atom

ENERGY LEVELS• According to the Schrodinger equation the energy level of a hydrogen-like

atom is given by the equation below. Given that R is equal to 2.17x10-18J, find the energy level of the n=1 and n=2 levels? What is the difference between these energy levels?

RYDBERG EQUATION: DERIVATION• IF THE ENERGY OF A GIVEN ENERGY LEVEL IS DEFINED AS EN=-RH(1/N2).

WE CAN FIND THE DIFFERENCE IN ENERGY SHELLS BY ENF-ENI

Either of these are often shown in text books. Use whichever you

prefer but be sure not to mix them up. One has a negative one does not.

Change= Final-initial

EMISSION/ABSORPTION SPECTRA

RYDBERG EXAMPLE

• I’ll do: • The energy levels of hydrogen-like one-electrons of atomic

number Z differ from those of hydrogen by a factor of Z2. Predict the wavelength of the transition from n=2 to n=1 in He+. (1.17)

RYDBERG EXAMPLE

A violet line is observed at 434 nm in the spectrum of atomic hydrogen. Determine the values of n for the beginning and ending energy levels of the electron during the emission of energy that leads to this spectral line.Hints:We are observing a line, therefore is a photon being absorbed or emitted?

Based on the answer to the above: is the final higher or lower than the initial? What does that mean about DE

The Balmer series is the hydrogen emission series that is in the visible region what does this mean about nf? (homework you could look up, on an exam I’d tell you).

• If we have all one type of atom, and we excite all of them to a particular energy level, what will be true of the emitted light?

A) The photons will all have the same wavelength

B) The photons have different wavelengths

C) No photons will be emitted

D) The photons will have different energies

E) I do not know

Reflected vs. Emitted

• Emitted light comes from a particular source. • Examples?

•Reflected light “bounces” off other objects

• Examples?

• Each time we think about light think about which it belongs too.

LASERS

• Light Amplification by Stimulated Emission of Radiation.

http://www.infoplease.com/images/ESCI112LASERS003.gif

Why can’t we see the laser light until it hits the wall?

WHAT DO WE USE EMISSION SPECTRA FOR?

Hydrogen Emission Spectra

Fe Emission Spectra

Given the above, and furthermore, that elements have specific emission spectra, what could we use spectroscopy of elements for?

WHAT DO WE USE EMISSION SPECTRA FOR?

• Emission Spectra is unique to individual elements

• Spectra can be collected and matched to known emission spectra to determine the element present.

• Flame tests

Hydrogen Emission Spectra

Fe Emission Spectra

Flame test

EMISSION SPECTRA: APPLICATIONS IN ASTRONOMY

•Spectra is collected•Compared to known ions•Temperatures known

SPECTROSCOPY

microscopyU

**don’t memorize this

GREEN FLUORESCENT PROTEIN (GFP)

Tsien

Anthony Chan, Emory University

Lets combine everything we know to think about some things.

TIME TO REGRESS TO OUR 5 YR OLD SELVES

•Why is the grass green?

THE GRASS IS GREEN BECAUSE…

What happens if you shine green light on the plants?

What happens if you shine red light on the plants?

TIME TO REGRESS TO OUR 5 YR OLD SELVES

•Why is the sky blue?

WHY IS THE SKY BLUE?

TIME TO REGRESS TO OUR 5 YR OLD SELVES

•Why is the Sun Yellow/Orange?

• (hint: is it really? Remember our black body radiation talk)

scienceblogs.com

WHY IS THE SUN YELLOW/ORANGE

WHY IS THE SKY BLUE?