Mendeleev published a Periodic Table in 1871 - OCR Gateway - GCSE Chemistry: Combined Science - Question 15 - 2020 - Paper 1

The Periodic Table on the Data Sheet demonstrates significant improvements over Mendeleev's original version in several key areas:

1. Arrangement by Atomic Number

Unlike Mendeleev's table which was primarily arranged by atomic mass, the new table organizes elements by atomic number. This arrangement resolves discrepancies where elements did not fit consistently based on their weights, leading to a more logical structure.

2. Inclusion of Noble Gases

The updated Periodic Table incorporates the noble gases, which were not known during Mendeleev's time. This addition highlights the completeness and accuracy of modern atomic theory.

3. Clear Grouping of Elements

The new table features well-defined groups and periods, reflecting trends in chemical properties more clearly. For example, alkali metals are distinctly grouped together, showcasing their similar reactivity, which Mendeleev's layout did not clearly illustrate.

4. Use of Lanthanides and Actinides

The inclusion of the lanthanide and actinide series in the modern table ensures that the transition elements are also highlighted, further organizing elements in a way that emphasizes their properties and behaviors in chemical reactions.

These improvements in the structure and organization make it easier to predict the properties of elements and their compounds.