Question

what physical and chemical properties of elements were used by man live in creating his periodic table?? list to observation which post a challenge to NASA live predict law​

Answer 1

The element were arranged on the basis of increasing atomic masses.

Physical Properties:

The atomic masses further influenced physical properties like melting point, density, boiling point, etc.

Chemical Properties:

Reaction with oxygen and chlorine.

Two observations which posed a challenge to Mendeleev's Periodic Law:

Position of the isotopes: The isotopes of the elements have different atomic masses. So, isotopes must occupy different positions in the periodic table.

Anomalous positions of some elements: In the periodic table put forward by Mendeleev, some elements with the higher atomic masses were placed before elements with lower atomic masses; say for example, Ar (atomic mass = 39.9) is placed before Potassium (K) (atmoic mass = 39.1)

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