For Lesson two, we've bundled together four webcast that focus on the period two
atoms. These webcasts are intended to build, strengthen and maintain your
foundation for organic chemistry. In 2.1, we'll introduce the elements of organic
chemistry. In Webcast 2.2, we'll talk about the very important stability trends
of charged species. The information in this webcast are going to be used
throughout the entire semester, and beyond. In 2.3, we'll introduce or maybe
re-introduce, the ideas of electron configuration of the organic elements. And
in 2.4, we'll talk about electron pairing and introduce the concept of electron-pair
domains. Alright. Let's get started. Living systems are dominated by the
chemistry of carbon as is apparent from the data in the chart that's shown here.
Whether we're talking about ancient biomass, crude petroleum, or tissue that's
derived from plants or humans in which water has been removed. It's apparent that
on a mass percent basis, carbon is the dominant element. The uniqueness of carbon
in living systems really only becomes apparent when we examine the elemental
composition in nonliving matter, for example, in the Earth's crust. From the
plot that you can see here, we'll find that silicon, oxygen, and aluminum
dominate the Earth's crust and we have to zoom in really far and it's even difficult
to find unless we swing it all the way around. The carbon is even present on any
significant degree. If we examine the elemental composition of the universe,
what we find in this case is that the predominant elements are hydrogen and
helium. And once again, carbon is almost nowhere to be found on this map. It's
really only living systems in which there's a significant amount of carbon
that's present. I think you can see that if you're interested in living systems,
it's the P block of the periodic table where all the action is at. We're going to
be especially interested in the second row, the period two elements, because
that's where carbon, nitrogen and oxygen are found. There's a couple of third row e
lements, phosphorous and sulfur, that are important. And of course, hydrogen is
important as well. And those are the main elements of organic compounds that we'll
be studying over the coming year. Where we're going from here is to begin to look
at some of trends in the periodic table. These trends are going to help us
understand the organic chemistry and they're going to play an important role
throughout the entire semester.