For n=1, 2(1)2 = 2. Ex. H cannot exceed a duet. QUESTION: Which of the following atoms can have more than an octet of valence electrons when it shares electrons with other atoms? A. S, B. N, C. C, D. H Size of valence shell determines how many valence electrons electrons can “surround” an atom. For atoms in the nth period, valence shell is nth shell and maximum number of electrons that can be assigned to the valence shell is 2n2. For n=1, 2(1)2 = 2. Ex. H cannot exceed a duet. For n=2, 2(2)2 = 8. (2 in the 2s subshell; 6 in the 2p subshell). Ex. C and N cannot exceed an octet. For n=3, 2(3)2 = 18. Ex. S belongs to third period Which of the following atoms can have more than an octet of valence electrons when it shares electrons with other atoms? A. S, B. N, C. C, D. H PAUSE CLICK The size of an atom’s valence shell determines the maximum number of valence electrons that can surround the atom when it shares electrons with other atoms. The outermost or valence of atoms belonging to the nth period is the nth shell. and the maximum number of electrons that can be assigned to this outermost shell is 2n squared For the first row elements, n equals 1. And 2n squared is 2 times one squared, or 2. Therefore, hydrogen cannot have more than two electrons surrounding them when they share electrons. Choice D is incorrect. Hydrogen cannot have more than an octet. It can’t even have more than a duet. For the second row elements, n equals 2. And 2n squared is equal to 8. Of these eight, we can imagine 2 electrons being assigned to the 2s subshell and 6 to the 2p subshell). Therefore, second row elements like carbon and nitrogen cannot have more than an octet. Choices B and C are incorrect. For atoms belonging to the 3rd row, in addition to the 3s and 3p subshell, there is also a 3d subshell. So the valence shell can accommodate up to 18 electrons. Therefore, Sulfur, which belongs to the third row can have more than eight valence electrons surround it when it shares electrons with other atoms. The correct answer is choice A... sulfur. CLICK CONTINUED ON NEXT SLIDE

Sulfate is an example of a structure where sulfur has more eight valence electrons surrounding it. In the structure, shown here, there are 12 valence electrons around the sulfur atom. This is one of several resonance structures for sulfate. This particular resonance structure is believed to be more significant than this one CLICK where all the bonds are single bonds and the sulfur atom has an octet around it. The reason is that the Sulfur atom on the left has a formal charge of zero, whereas the sulfur atom on the right has a formal charge of +2.

Video ID: 3-9-1 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08