Structure of the Periodic Table (College Board AP® Chemistry) : Study Guide
Structure of the Periodic Table
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
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