Question

Write short notes.
a. Mendeleev's periodic law.
b. Structure of the modern periodic
table​

Answer 1

a. the law that the properties of the elements are periodic functions of their atomic numbers. Also called Mendeleev's law. (originally) the statement that the chemical and physical properties of the elements recur periodically when the elements are arranged in the order of their atomic weights.Mendeleev realized that the physical and chemical properties of elements were related to their atomic mass in a 'periodic' way, and arranged them so that groups of elements with similar properties fell into vertical columns in his table. ... And when they were discovered, Mendeleev turned out to be right.

In 1869, after the rejection of Newlands Octave Law, Mendeleev Periodic table came into the picture. In Mendeleev's periodic table, elements were arranged on the basis of the fundamental property, atomic mass, and chemical properties. During Mendeleev's work, only 63 elements were known.

b.Structure of the Modern Periodic Table. The Modern Periodic Table is arranged in order of increasing atomic number, which is the number of protons in the nucleus of an atom. The lightest atom is Hydrogen, in the upper left-hand corner, with an atomic number of 1.The periodic table also has a special name for its vertical columns. Each column is called a group. The elements in each group have the same number of electrons in the outer orbital. Those outer electrons are also called valence electrons.

Answer 2

Explanation:

Mendeleev's periodic table was based on atomic weight. In 1913, Moseley from his studies on X-rays found that the atomic number is the more fundamental property of an element than its atomic mass. ... In the Mendeleev's periodic table the subgroups A and B have been kept together giving rise to short periods.