Mendeleev's grouping is supported by similarities in appearance, melting, and boiling points, but inconsistencies in conductivity and the properties of iodine challenge his concept of strict periodicity.
Mendeleev's organization of elements into groups was based on similarities in physical and chemical properties. Analyzing the data in the table, several aspects support Mendeleev's grouping while others present challenges.
Melting and Boiling Points:
Mendeleev observed that elements in the same group tend to have similar physical properties. The data for chlorine, bromine, and iodine, all halogens in the same group, shows a progressive increase in melting and boiling points, supporting Mendeleev's idea.
Similarly, lithium, sodium, and potassium, alkali metals in the same group, display a consistent trend of decreasing melting and boiling points.
Appearance at Room Temperature:
Mendeleev considered the appearance of elements. The halogens (chlorine, bromine, iodine) share a similar appearance at room temperature, reinforcing their placement in the same group.
The alkali metals (lithium, sodium, potassium) also share a shiny appearance, supporting their grouping.
Conductivity:
Mendeleev likely considered electrical conductivity. The alkali metals all conduct electricity, aligning with Mendeleev's grouping. However, the halogens do not conduct electricity, which presents a deviation.
Inconsistencies:
The significant difference in melting and boiling points between iodine and the other halogens challenges Mendeleev's concept of strict periodicity.
In summary, Mendeleev's grouping is supported by similarities in appearance, melting and boiling points within each group. However, the variation in conductivity among halogens and the notable anomaly in iodine's physical properties highlight some inconsistencies in Mendeleev's initial organization.
