Basic chem

1. The work function of potassium is 3.68 x 10-­‐19 J. a. What is the minimum frequency of light needed to eject electrons from the

metal? b. Calculate the kinetic energy of the ejected electrons when light of frequency

equal to 8.62 x 1014 s-­‐1 is used for irradiation.

2. Thermal neutrons are neutrons that move at speeds comparable to those of air molecules at room temperature. These neutrons are most effective in initiating a nuclear chain reaction among 235U isotopes. Calculate the wavelength (in nm) associated with a beam of neutrons moving at 7.00 x 102 m/s (mass of neutron = 1.675 x 10-­‐27 kg)

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3. The blue color of the sky results from the scattering of sunlight by air molecules. The blue light has a frequency of about 7.5 x 1014 Hz.

a. Calculate the wavelength, in nm, associated with this radiation

b. Calculate the energy, in joules, of a single photon associated with this frequency

4. When an intense beam of green light is directed onto a copper surface, no electrons are ejected. What will happen if the green light is replaced with red light?

5. The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 x 103 km.s-­‐1. What is the wavelength of the ejected electron?

6. Alarm systems employ the photoelectric effect. Typically, a light beam is aimed at a sample of Na, producing a photoelectric current. An intruder blocks the beam, thereby

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turning off the current, and triggering the alarm. Given that the work function of Na is 4.41 x 10-19 J particle-1, what is the longest wavelength of light (in nm) that can be used in the alarm system?

7. A certain cation Xn+ has an electron configuration of [Ar]3d5. Answer the following: a) What type of element is X? b) The reaction of X with chlorine gas proceeds as following: 2X(s) + 3Cl2(g) à 2XCl3(s) Given this, determine n+ c) Now that you know the charge of the cation, determine the identity of X.

8. Draw the lewis dot structure give the molecular shape

Moleule Lewis structure Electronic geometry Molecular geometry (shape)

SeH2

NCl3

PCl5

OBr2

CO32-­‐

CCl4

9. Give the full ground state electron configuration and the abbreviated noble gas)

configuration for the following elements and or ions: a) C ___________________________________ _____________________________

b) Se2+ ___________________________________ _____________________________

c) Fe ___________________________________ _____________________________

d) P ___________________________________ _____________________________

e) Tc ___________________________________ _____________________________

Name:____________________________________________________________ f) Cr ___________________________________ _____________________________

g) Cu ___________________________________ _____________________________

h) Ho ___________________________________ _____________________________

g) Cr+ ___________________________________ _____________________________

h) Cl-­‐ ___________________________________ _____________________________

10. Which of the following combinations of quantum numbers are allowed for an

electron? Which are not? What would you change to make the ones that are not

possible be possible?

a. n=2 l=2 ml=1 ms =1/2

b. n=3 l=1 ml=0 ms =-­‐1/2

c. n=5 l=1 ml=2 ms =1/2

d. n=4 l=-­‐1 ml=0 ms =1/2

11. Label the orbital described by each of the following sets of quantum numbers

a. n=4 l=1 à orbital _________________

b. n=2 l=0à orbital _________________

c. n=6 l=3à orbital _________________

d. n=5 l=2à orbital _________________

12. What are the principal (n) and orbital angular momentum (l) for each of the following:

a. 6p n= ________ l= ________

b. 3d n= ________ l= ________

c. 2p n= ________ l= ________

d. 5f n= ________ l= ________

e. 2s n= ________ l= ________

f. 6f n= ________ l= ________

g. 4d n= ________ l= ________

h. 5p n= ________ l= ________

13. How many electrons can have the following quantum numbers in an atom:

a. n = 2, l=1 ____________

b. n = 5, l=3, ml=-1 ____________

c. n = 2, l=1, ml=0 ____________

d. n = 7 ____________

14. The 3 quantum numbers for an electron in a hydrogen atom in a certain state are n=4, l=2, ml=1. The electron is located in what type of orbital?