Question

What are the three main classes of elements in the periodic table?

Answer 1

Periodic table makes things easy for us as it has the elements arranged in such a beautiful manner. That it becomes easier to study their physical, chemical and all other properties. In modern periodic tables the elements are placed in increasing order of their atomic number. Atomic number of an element is the total count of protons in its nucleus.

Complete answer:
Periodic table has seven periods and eighteen groups.

Period	Number of elements
First	Two
Second-third	Eight
Fourth-fifth	Eighteen

Sixth and seventh period are the longest periods each having thirty two elements.
On the basis of groups blocks are defined as: First- Second-s-block elements, third- twelveth –d-block, thirteen-eighteen are p-block elements.
These blocks are the main classification of elements which contains: METALS, METALLOIDS, NON-METALS.
s-block contains metals, d-block along with metals have metalloids, p-block along with non-metals contains metalloids.
Metals have properties like ductility, malleability, shine and good conductors of both heat and electricity.
Non-metals: They appear very dull, bad conductor of heat and electricity but they are very useful ex: plastic, rubber.
Metalloids: They inherent properties of both metals and nonmetals, conduct moderate heat and electricity.

Note:
We also have f-block (inner transition elements) which contains actinides and lanthanides.