Tuesday, September 23rd, 2014

PES – a first attempt at creating a question

As those of us teaching the new AP chemistry curriculum for the first time struggle with the lack of example material and sample questions released by the College Board, we are left to our own devices in terms of generating questions relating to the new topics. I have already taught the new, PES part of the course and have tested it. As part of my attempts to guess what may be asked, and to guess how it may be asked, I produced the question shown below as part of my assessment. With so little to go on this is STRICTLY a ‘first guess’/’first draft’ so I would love to hear your criticisms and comments.

The simulated plots were created using Thomas Silak’s Excel spreadsheet – many thanks Thomas!

 

PES Question

My answers:

(a) The x, y and z groups represent the sub-shells 1s, 2s and 2p respectively that are occupied in both atoms.

(b) Carbon’s 1s electrons (i.e., those represented by the ‘x peak’) are subjected to a greater Coulombic force than boron’s 1s electrons, since carbon has six protons as opposed to boron’s five.

(c) The ‘z peak’ is the peak created by the electrons in the 2p sub-shell and the height of the peak is determined by the number of electrons in that sub-shell. Boron has only one, 2p electron whereas carbon has two, 2p electrons.

(d)(i) It would be the left of carbon’s ‘x peak’, at a higher energy since nitrogen’s seven protons (as opposed to carbon’s 6), exert a greater Coulombic attraction meaning it requires more energy to remove them.

(ii) The ‘z peak’ is the peak created by the electrons in the 2p sub-shell and the height of the peak is determined by the number of electrons in that sub-shell. Nitrogen has three, 2p electrons whereas carbon only has two, 2p electrons. Nitrogen’s ‘z peak’ will be 1.5 times as big as carbon’s ‘z peak’.

(e)(i) 1s electrons

(ii) 2s electrons

(iii) 2p electron