The Periodic Table (DP IB Chemistry) : Revision Note

The Periodic Table

• The Periodic Table is a list of all known elements arranged in order of increasing atomic number, from 1 to 118

• In addition, the elements are arranged so that atoms with the same number of shells are placed together, and atoms with similar electronic configurations in the outer shell are also placed together

  • This is achieved as follows:

    • The elements are arranged in rows and columns

    • Elements with one shell are placed in the first row (i.e. H and He)

    • Elements with two shells are placed in the second row (Li to Ne) and so on

• A row of elements thus arranged is called a period

  • The period number, n, is the outer energy level that is occupied by electrons

• In addition, the elements are aligned vertically (in columns) with other elements in different rows, if they share a similar outer-shell electronic configuration

  • The outer electrons are known as the valence electrons

  • A column of elements thus arranged is called a group

The Periodic Table

The Periodic Table showing the groups and periods

• Since the electronic configurations of H and He are unusual, they do not fit comfortably into any group

• They are thus allocated a group based on similarities in physical and chemical properties with other members of the group

  • He is placed in Group 0 on this basis

  • Hydrogen does not behave like any other element and so is placed in a group of its own

Diagram to show the s, p and f blocks in the Periodic Table

The blocks of the periodic table

• All elements belong to one of four main blocks: the s-block, the p-block, the d-block and the f-block

  • s-block elements contain only s electrons in the outer shell

  • p-block elements contain at least one p-electron in the outer shell

  • The d-block elements are all those with at least one d-electron and at least one s-electron but no f or p electrons in the outer shell (up to 5d)

  • The f-block elements are all those with at least one f-electron and at least one s-electron but no d or p electrons in the outer shell

• The physical and chemical properties of elements in the periodic table show clear patterns related to the position of each element in the table

  • Elements in the same group show similar properties, and properties change gradually as you go across a period

• As atomic number increases, the properties of the elements show trends which repeat themselves in each period of the periodic table

  • These trends are known as periodic trends and the study of these trends is known as periodicity