Chemistry · Periodic Classification Of Properties · NEET
There are more than 118 known elements, and each forms many compounds. Studying every element and every compound one by one would take a lifetime. NCERT says the same: with so many elements it is 'very difficult to study individually the chemistry of all these elements.' Classification groups similar elements together, so learning one member teaches you a lot about the whole group. This saves huge time in NEET prep.
It means putting elements into groups based on shared properties. Elements that behave in a similar way (like reacting with water the same way, or forming the same kind of oxide) are placed in the same vertical column, called a group. This ordered arrangement is the periodic table. So 'classification' just means sorting elements into a smart, repeating pattern.
Because properties repeat in a regular pattern as you move across the table. If you know an element's position, you can guess its valency, the type of oxide it forms, and which family it belongs to. Mendeleev famously left gaps and predicted the properties of elements not yet discovered, and later they were found matching his predictions. In NEET, you use this to predict things like the family of element Z = 114 without ever seeing it.
The MODERN classification is based on atomic NUMBER (number of protons). Mendeleev first used atomic weight, but that gave a few wrong orders. The Modern Periodic Law fixed this: 'The physical and chemical properties of the elements are periodic functions of their atomic numbers.' This is a common NEET trap, so remember: modern = atomic number.
Because it organizes ALL elements into one page where position tells you behavior. From an element's spot you can read off its group, block, metal or non-metal nature, and rough reactivity. It turns a huge memory task into a pattern task. This is why nearly every NEET periodicity question starts from an element's position in this table.
The element Z = 114 has been discovered recently. It will belong to which of the following family/group and electronic configuration?
Magnesium reacts with an element (X) to form an ionic compound. If the ground state electronic configuration of X is 1s2 2s2 2p3, the simplest formula for this compound is:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
More than 118 elements are known. NCERT (older text) mentions 114; the newest elements are man-made and made in labs. The exact count is less important than the idea: there are too many to study one by one, which is why we classify them.
Dmitri Mendeleev is called the father of the periodic table. He arranged elements by atomic weight and boldly left gaps for undiscovered elements, predicting their properties. Later the table was improved to use atomic number, giving the Modern Periodic Law.
Yes. Almost every periodicity question (atomic radius, ionization enthalpy, oxide nature, family of an element) is solved using the element's position in the classified table. Understanding WHY we classify makes the whole chapter feel like one connected system instead of random facts.
So we can predict the properties of any element (even a brand-new one) from its position, instead of memorizing every element separately. Classification turns memory work into pattern work.
