Structure of the Periodic Table (College Board AP Chemistry)

• The periodic table is a tabular arrangement of chemical elements organized based on their increasing atomic number, from 1 to 118
• The periodic table is organized into horizontal rows called periods and vertical columns called groups

The Periodic Table

• Periods represent the principal energy shells of an element
• Groups are columns that share similar chemical properties due to the number of valence electrons

The Structure of the Beryllium Atom

The beryllium atom in the periodic table

• The periodic table is divided into four block types: s-block, p-block, d-block, and f-block
  • s-block elements have only s electrons in their valence shell
  • p-block elements have at least one p-electron in their valence shell
  • d-block elements have at least one d-electron and one s-electron, but no p or f electrons in their outer shell (up to 5d)
  • f-block elements have at least one f-electron and one s-electron, but not p or f electron in their outer shell

Blocks in the Periodic Table

s-block, p-block, d-block, and f-blocks in the Periodic Table

Electron Configurations

• The arrangement of electrons in the energy shells and subshells of an atom is described by its electron configuration
• The electron configuration of an element can be predicted by using the periodic table
• The image below shows how this can be done for the germanium atom:

Electron Configuration of the Germanium Atom

Deducing the electron configuration of germanium as 1s², 2s², 2p⁶, 3s², 3d¹⁰, 4s², 4p² 

• Germanium is in the Group 4 (skipping the transition metals) and in Period 4
• Group 4 tells you that it has 4 valence electrons
• Period 4 tells you that it has the 4 valence electrons in the fourth shell
• Finally, germanium is in the second position of the p-block of the periodic table, therefore, two electrons must be in the p subshell