Intensive Chemistry Seminar – Fall 2007
worksheet #6







1.	Give a physical description of electric potential energy on the atomic level.  Hint:
	think about how you would describe potential energy on a macroscopic level.




2.	Is electric potential energy, V, an observable?  What does it allow us to predict?




3.	 The electron in a hydrogen atom is initially at a distance 1 Å from the proton and 
	then moves to a distance 0.5 Å from the proton.
 
	(a) Calculate the change in the force between the proton and the electron.

	(b) Calculate the change in the potential energy between the proton and the 	  	      electron.

	(c) Calculate the change in the velocity of the electron.

4.	Potential energy diagrams are a very useful tool for describing the interaction of 	electrons and protons on the atomic level.  Create a plot of potential energy (in 	eV) versus distance (in Å) for the following pairs: proton-proton, electron-
	electron, electron-proton.  For each pair plot 3 points to help you determine the
	shape and location of the potential energy curve.  












5.	Referring to the diagram you created in problem 6, describe the relationship 
	between potential energy and force.  Be specific (i.e. provide a formula relating F 
	to V) and at two points on each curve draw this relationship.





6.	The motion of the electron in the hydrogen atom is described by its total energy, 
	E, (E = kinetic energy + potential energy).  Write down the formula for E.  
	Calculate the total energy necessary in order for the electron to have velocity 
	equal to 0.2c (1/5 the speed of light).








7.	As mentioned in the text, it is often instructive to draw a straight line on a 
	potential energy diagram to represent a constant total energy.  Redraw your 	potential energy curve for the electron-proton pair and include a constant total 
	energy line for E > 0.  Now, at 4 points, draw lines connecting the potential 
	energy to the total energy.  What do these lines represent?  Why?  Is the electron 
	bound for this total energy? Why or why not?












8.	Repeat problem 9 for E < 0.







9.	Describe the difference between the bound and unbound motion of the electron in 
	the hydrogen atom.  Is it possible to remove an electron from a bound state?  If so, 
	how?




10.	Define first ionization energy and second ionization energy.  How does the first 
	ionization energy of an element compare with its second ionization energy?  	Why?




11.	In the reaction:    X(g)   X+(g) + e -  an addition of energy to the initial state is 	required to remove an electron.  Why is energy needed to free the electron?



12.	What column contains elements with the highest overall ionization energies?  	What does this say about these elements?




13.	Estimate the second ionization energy of hydrogen.



14. 	For each of the following pairs of atoms, state which you expect to have the 	higher first ionization energy: 							(a) Rb or Sr; (b) Po or Rn; (c) Xe or Cs; (d) Ba or Sr.



15.	True or False: (if False explain why)
a.First ionization energy is always negative.
b.Ionization energy is a measure of the stability of the atom.
c.ΔE > 0 if a process liberates energy.



16.	For a given element there are easy and hard ionization energies.  What does this 	suggest about the structure of the atom?