AP Chem Mass Spec and PES

AP Chem
Mass Spectroscopy Review and Photo Electron Spectroscopy

• Relative intensity of particles with varying mass to effective charge (isotopes/molecules)

• Average atomic mass estimated from mass spec data

• Solid, liquid or gas sample is ionized;

• Ions are separated according to mass to charge ratio

Mass Spec Refresher 1

• The mass spectrum of a sample containing a single pure element gives information about the naturally occurring isotopes of that element. By reading a mass spectrum, you can determine the isotopic masses (x- axis) as well as the relative abundances of those isotopes (y-axis)

Mass Spec Refresher 2

• Convert the precent abudances to decimals and multiply them by the mass of each isotope and add the results together.

  • Check your notes for a refresher on how to do this.

Calculating the mass

Multiple Choice

Based on the mass spectrum of atom Y, which of the following statements is false?

• Peak A and peak D come from atoms that have the same number of electrons

• There are seven isotopes of atom Y

• Peak C comes from the most abundant isotope of atom Y

• Peak D comes from an atom with 4 more protons than the atom that gave peak B

Multiple Choice

The identify of Element Y is most likely which of the following

• Zirconium (Zr)

• Molybdenum (Mo)

• Americium (Am)

• 1. Einsteinium (Es)

Hotspot

Click on the dot above the isotope that contains the highest number of neutrons

Reorder

Based on the mass spectrum on the left order the isotopes from least abundant to most abundant.

• 61 amu

• 62 am

• 60 amu

• 58 amu

1

2

3

4

• 1
• 2
• 3
• 4

Photoelectron Spectroscopy (PES)

Photoelectron spectroscopy analyzes the kinetic energy distribution of the emitted photoelectrons to study the composition and electronic state of a sample.

What is PES?

1. The sample is exposed to electromagnetic radiation (typically x-ray or UV photons)

2. Electrons jump off of the surface of a sample and go through an analyzer

   1. This process can be described as photoionization.

How does is PES work?

The PES graphs directly correspond to the electron configuration.

What does is PES tell us?

• The graph on the right shows the PES for Si

  • 1s²2s²2p⁶3s²3p²

​1s²

​2s²

​2p⁶

​3s²

​3p²

​How to Read a PES

​The taller the peak the more electrons represented

2p⁵

2s²

1s²

• The Energy is much is needed to remove an electron. That's the “binding energy” a.k.a ionization energy

• The higher the "binding energy" the close the orbital is to the nucleus

Each peak represents a single orbtial type, the 1s is closest to the nucleus.

Labelling

Label the peaks with the correct orbital type. Pay attention to the values on the x-axis. The peak farthest to the left is well above 100000 kJ*mol^-1 and the one on the right is well under 1000 kJ*mol^-1

Drag labels to their correct position on the image

3s

3p

2s

1s

2p

Math Response

How many electrons are shown in this PES?

Type answer here

Correct Answer: 6

Deg^°

Rad

Fill in the Blanks

Multiple Choice

Based on this PES which energy level is the valance level for this element?

• The 1st energy level

• The 2nd energy level

• The 3rd energy level

• There's not enough data to tell

Hotspot

Click on all of the peaks that represent core electrons in this PES

Multiple Choice

This question is just to round out the assignment to 10 points.

• This is the right answer.

• Don't click here

• Or here

• If you select this you throw away a point