What physical and chemical properties of elements did Mendeleev consider in compiling the periodic table? What challenges did Mendeleev face in following periodic law?
The physical property used was the atomic mass of an element.
The chemical property used was the nature of oxide and hydride formed( i.e. similarity in chemical properties was used by Mendeleev).
The two observations that posed challenges in Mendeleev's Periodic Law were:
(i) In certain pairs of elements, the increasing order of atomic masses was not obeyed. In these, Mendeleev placed elements according to similarities in their properties and not in increasing order of their atomic masses.
for example: The atomic mass of argon is 39.9 and that of potassium 39.1. But argon is placed before potassium in the periodic table.
(ii) Isotopes are the atoms of the same element having different atomic masses.Therefore, according to Mendeleev’s classification these should be placed at different places depending upon their atomic masses. For example, hydrogen isotopes with atomic masses 1, 2 and 3 should be placed at three places. However, isotopes have not been given separate places in the periodic table because of their similar properties.
The physical property used was the atomic mass of an element.
The chemical property used was the nature of oxide and hydride formed( i.e. similarity in chemical properties was used by Mendeleev).
The two observations that posed challenges in Mendeleev's Periodic Law were:
(i) In certain pairs of elements, the increasing order of atomic masses was not obeyed. In these, Mendeleev placed elements according to similarities in their properties and not in increasing order of their atomic masses.
for example: The atomic mass of argon is 39.9 and that of potassium 39.1. But argon is placed before potassium in the periodic table.
(ii) Isotopes are the atoms of the same element having different atomic masses.Therefore, according to Mendeleev’s classification these should be placed at different places depending upon their atomic masses. For example, hydrogen isotopes with atomic masses 1, 2 and 3 should be placed at three places. However, isotopes have not been given separate places in the periodic table because of their similar properties.
