How was mendeleev's scheme for listing elements different from that used in the modern periodic table?

Answer 1

Mendeleev's scheme was different from the modern Periodic Table because he listed the elements in order according to the relative Atomic Mass. Dmitri Mendeleev created his periodic table in 1868.

Answer 2

Since not all was known about the structure of an atom, Mendeleev assumed that it was its mass number that determined the properties of each element. He arranged the known elements from left to right according to the increasing atomic mass, and in columns according to similar properties. He was also smart enough to leave an empty space each time the next element did not match the properties of the elements in that particular column. He predicted that there would be more elements discovered that would fit into those blank spaces at some point in the future.

When the more detailed structure of the atom was known, it became obvious that it was the number of protons, known as the atomic number, that was responsible for the properties of the elements. The modern periodic table is arranged in rows according to the increasing atomic number, and in columns according to similar properties. In many cases, as the atomic number increases, the mass number also increases, but there are a few exceptions. For example, iodine's atomic mass is slightly smaller than the mass of tellurium, however, iodin's atomic number is greater than that of tellurium.

Answer 3

The modern chart sequence is is based on the atomic number, which is actually the factor that figures the number of electrons, and therefor the properties that are periodic. At the time of Mendeleev, nothing was known of protons, neutrons, and electrons, and there was no atomic number. Mendeleev noticed the periodicity of certain elemental properties seemed to follow atomic weight. So, he based his chart on that. Atomic weight follows atomic number somewhat, but varies depending on the number of neutrons in the most common isotope. This becomes more pronounced the further you progress down the chart.

Of course, the listed elements on each chart differ as well. Many elements were unknown or not known to be elements back in Mendeleev's day.

Answer 4

Mendeleev arranged the elements in the increasing order of their atomic masses. In the modern periodic table, the elements are arranged in the increasing order of the atomic numbers.

The f block elements present in the modern table were not discovered during Mendeleev's time and are absent in Mendeleev's table.

Answer 5

Modern periodic table is arranged according to the atomic numbers of elements and Mendeleev's periodic table was arranged according to the atomic masses of elements.

Answer 6

Mendeleev's table was arranged in order of increasing atomic mass. Modern periodic table is arranged in order of increasing atomic number.