Class 10 - Science

Class X (2026-27)
Science 086
Unit 1
Periodic Classification of Elements
In Class IX we have learnt that matter around us is present in the form of elements,
compounds and mixtures and the elements contain atoms of only one type. Do you
know how many elements are known till date? At present, 118 elements are known to
us. All these have different properties. Out of these 118, only 94 are naturally occurring.
As different elements were being discovered, scientists gathered more and more
information about the properties of these elements. They found it difficult to organise all
that was known about the elements. They started looking for some pattern in their
properties, on the basis of which they could study such a large number of elements with
ease.
1.1 Making Order Out Of Chaos–Early Attempts at the Classification of Elements. We have been learning how various things or living beings can be classified on the basis of their properties. Even in other situations, we come across instances of organisation based on some properties. For example, in a shop, soaps are kept together at one place while biscuits are kept together elsewhere. Even among soaps, bathing soaps are stacked separately from washing soaps. Similarly, scientists made several attempts to classify elements according to their properties and obtain an orderly arrangement out of chaos.
The earliest attempt to classify the elements resulted in grouping the then known elements as metals and non-metals.

Later further classifications were tried out as our knowledge of elements and their properties increased.