IB Chemistry - Periodicity

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Syllabus ref: 3.1

The periodic table shows all of the elements arranged in order of increasing atomic number. Mendeleev (among others) first noticed that certain element characteristics or properties tended to repeat in specific intervals. The idea of 'periodic repetition of properties' lead to the table being known as the periodic table of the elements.

Nature of science:

Obtain evidence for scientific theories by making and testing predictions based on them-scientists organize subjects based on structure and function; the periodic table is a key example of this. Early models of the periodic table from Mendeleev, and later Moseley, allowed for the prediction of properties of elements that had not yet been discovered.


The periodic table is arranged into four blocks associated with the four sublevels- s, p, d, and f.

The periodic table consists of groups (vertical columns) and periods (horizontal rows).

The period number (n) is the outer energy level that is occupied by electrons.

The number of the principal energy level and the number of the valence electrons in an atom can be deduced from its position on the periodic table.

The periodic table shows the positions of metals, non-metals and metalloids.

Applications and skills

Deduction of the electron configuration of an atom from the element's position on the periodic table, and vice versa.

In Chapter 5.1