Question

What are achievements of Mendeleev’s periodic table? What was the basis of classifications of elements in it?

Answer 1

Hint: The periodic table is defined as a tabular array of the chemical elements organized by atomic numbers, from the element starting with the lowest atomic number, hydrogen, to the element with the highest atomic number, oganesson.

Complete answer:
Mendeleev provided some blank spaces for those elements, which he predicted to be discovered in the future. Moreover, noble gases could be put together in a separate group, without affecting the proposed order. The formula of the hydroxides and oxides which were formed by element was used to determine the characteristics of that particular element.
According to Mendeleev’s Periodic table, atomic weight of a particular element was the basis of the properties it exhibit
A periodic table includes 7 horizontal rows as well as and 18 vertical groups.
We know that an electron in an atom is characterised by a set of four quantum numbers (n, I, m and s) where the principal quantum number (n) defines the main energy level known as the shell. We also know about how the electrons get filled into different subshells (s, p, d and f) inside the atom. For locating an element in the periodic table, it is reflected by the quantum numbers of the last orbital that is filled. Here we will discuss the direct relation between the electronic configuration of the element and its location in the periodic table. The atomic number of an element is defined as the number of protons present in the nucleus of an atom of that element.

Note:
The period indicates the value of n for the outermost or valence shell. In other words, a successive period in the periodic table is related to the filling of the next principal energy level, higher in number like n = 1, n = 2, n = 3.. refers to the filling of the first, second, third and higher principal energy levels. It can be readily observed that the number of elements in each period is twice the number of atomic orbitals available in the energy level that is being filled.