Question

A section which was common in Newland's and Mendeleev's classification is shown below :

Li	Be	B	C	N	O
Na	Mg	Al	Si	P	S

(i) Comment whose classification was better and why?
(ii) Give the point of difference (atleast two) between these two system of classification.

Answer 1

Part 1: Mendeleev's Periodic Table

1. Mendeleev arranged the 63 elements known at that time in the increasing order of their atomic masses.
2. He proposed that the properties of elements are a periodic function of their atomic masses.

Part 2: Newland's Law of octaves

1. The elements known were arranged according to their increasing atomic masses.
2. It suggests that every eighth element had the property similar to that of first element.

Part 3: Better classification:-

1. Mendeleev's classification was better than Newlands law.
2. This was because Newlands law was only applicable upto Calcium, but there was no such limitation in Mendeleev's classification.

Final answer:-

(i) Mendeleev's classification was better than Newland's due to Newland's applicability.

(ii)

Mendeleev's Classification	Newland's Classification
(i) Elements present in the groups had similar properties	(i) Every eighth element had similar properties(Newland's Octave law)
(ii) Left gaps for elements that he would predict be discovered later.	(ii) Only included elements known at that time.