Elements in the same horizontal row are in the same period. The periods are numbered from top to bottom. The period number is the same as the number of occupied electron shells.

The “lead” of a pencil is actually made of a substance called graphite which is made of carbon atoms. The picture shows a close-up of one carbon atom. A hydrogen atom has one proton as the nucleus and ...

In the n-type layer, there is an excess of electrons, and in the p-type layer, there is an excess of positively charged holes (which are vacancies due to the lack of valence electrons ... 1, closeup).