The molecular world
The molecular world

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course

The molecular world

3.3 Electronic configurations and the Periodic Table

Figure 21 has been designed for use in a particular thought experiment. The purpose of the thought experiment is to see how the electronic configuration of the atoms changes as one moves through the Periodic Table from beginning to end. We start with the hydrogen atom, which has one proton and one electron. Then we proceed through a series of stages in each of which we add one new proton to the nucleus, and one new electron to the clutch of surrounding electrons. At each stage, the filling order of Figure 21 tells us what sub-shells are occupied, and how many electrons those occupied sub-shells contain. In addition, the filling of successive sub-shells in this thought experiment generates the form of the Periodic Table shown in Figure 22, in which the winding arrowed pathway follows the filling order of Figure 21. The different blocks of elements span regions in which particular types of sub-shells are being filled up. With the typical elements, the sub-shell type is either s or p; in the case of the transition elements, with rows of ten, it is d; for the lanthanides and actinides, with rows of fourteen, it is f. Indeed, because of this connection, one can think of Figure 22 as a demonstration of how the filling order of Figure 21 can be deduced from the form of the Periodic Table.

Figure 22
Figure 22 The winding pathway shows how the order of sub-shell filling (Figure 21) generates the full Periodic Table. Elements in the same column usually have similar outer electronic configurations. Hydrogen has been juxtaposed with helium to indicate the filling of the 1s sub-shell

Click to view larger version of Figure 22

View document [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)]

Skip Your course resources

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371